Oculocutaneous albinism

Unravelling the molecular mechanisms and immune landscape of vitiligo: a comprehensive bioinformatics study on melanogenesis-related genes

BACKGROUND

Vitiligo is an autoimmune disorder marked by melanocyte destruction and skin depigmentation.

AIM

To explore the molecular mechanisms underlying melanogenesis and their link to vitiligo.

SUBJECTS AND METHODS

We analysed three vitiligo-related datasets, correcting for batch effects with ComBat. Key melanogenesis genes were pinpointed using LASSO and logistic regression, and a nomogram was developed. The immune microenvironment was evaluated by ssGSEA, and correlations between gene expression, melanogenesis pathways, and immune cell infiltration were examined.

RESULTS

We identified 2,405 DEGs, with 960 up-regulated and 1,445 down-regulated genes in vitiligo samples. GSVA indicated significant disturbances in melanogenesis pathways. ssGSEA revealed reduced activity in REACTOME_MELANIN_BIOSYNTHESIS and KEGG_MELANOGENESIS pathways. Three key diagnostic genes (CALM2, KIT, OCA2) were found and used to build a highly accurate predictive nomogram. Immune cell analysis showed increased T helper and Th2 cells in vitiligo, correlating with both diagnostic genes and melanogenic pathways.

CONCLUSION

This study identifies crucial melanogenesis-related genes and provides a predictive model for vitiligo risk. It underscores the relationship between impaired melanogenesis and immune cell infiltration, suggesting potential therapeutic targets.

Multiplexed Assays of Variant Effect and Reclassification of TYR Variants in Chinese Patients with Oculocutaneous Albinism

Oculocutaneous albinism type 1, caused by mutations in the tyrosinase gene TYR gene, is the most common form of albinism worldwide. Owing to the variants of uncertain significance (VUSs) classified by the American College of Medical Genetics and Genomics guidelines, patients who carry these VUSs do not receive a definitive molecular diagnosis. To clarify the pathogenicity of the VUS variants, we conducted multiplexed assays of variant effect to reclassify the TYR VUS variants. Protein expression, melanin production, enzyme activity, and subcellular localization were applied to 46 selected variants: 27 VUSs from 1243 patients with albinism, 14 pathogenic/likely pathogenic, and 5 benign/likely benign control variants. Odds of pathogenicity values were calculated as recommended by Brnich et al (2019). By conducting multiplexed assays of variant effect, PS3_moderate or PS3_supporting evidence was applied. By following the American College of Medical Genetics and Genomics guidelines, 25 of 27 VUSs were reclassified as likely pathogenic, and 3 of 11 likely pathogenic variants were reclassified as pathogenic. Therefore, 19 of 20 (95%) previously undiagnosed patients had a molecular diagnosis of oculocutaneous albinism type 1. In addition, the pathogenic mechanisms of TYR have been elucidated and categorized. These comprehensive multiplexed assays of variant effect provide a robust approach for curating TYR VUS. This study advocates multiplexed assays of variant effect for validating an accurate genotype-phenotype relationship.

Why humans evolved blue eyes

A surprising number of humans are equipped with a subpar eye model-featuring pale, colorful irides that are nowhere as good as the original dark ones at guarding the retina from sunlight and do, in fact, raise one's risk of eye disease. Here I apply evolutionary theory to understand why. I propose that the allele for human blue eyes, which arose just once, managed to spread from one individual to millions at an astonishing speed because it is a greenbeard. "Greenbeards"-imaginary genes, or groups of genes, that produce both a green beard and a behavior that favors other bearers of a green beard-have been deemed exceedingly unlikely to show up in the real world. And yet, as individuals who prefer blue eyes are more inclined to mate with blue-eyed partners and invest in blue-eyed offspring, any blue-eye preference (whether random or arising from the bias for colorful stimuli shared by all recognition systems) becomes rapidly linked to the blue-eye trait. Thus, blue eyes gain an edge by working like a peacock's colorful tail and a nestling's colorful mouth: twice self-reinforcing, "double runaway" evolution via sexual and parental selection. The blue-eye ornament gene, by binding to a behavior that favors other bearers of the blue-eye ornament gene, is ultimately recognizing and helping copies of itself in both kin and strangers-and greatly prospering, just like theory predicts.

Typical presentation of autosomal recessive oculocutaneous albinism in two siblings

Objective

We report the case history and clinical findings in two siblings, a 13-year-old male and a 10-year-old female, who presented with complaints of poor vision since childhood. Both children had blonde hair and depigmented skin.

Methods

Ocular examination revealed white eyebrows, white eyelashes, diminished vision in all eyes, hypochromic irides and pendular nystagmus. On dilated fundus examination, hypopigmented fundi with conspicuously visible choroidal vessels were noted. No foveolar reflex could be discerned and spectral domain optical coherence tomography (SD-OCT) of the macula showed an absence of the foveal pit in all four eyes. On pedigree charting the subjects were the 2nd and 3rd offspring of a non-consanguineous married couple. One of the mother's siblings and one of the grandmother's siblings also had a similar disorder.

Results

The poor definition of the foveal pit at the centre of the macula, i.e. foveal hypoplasia, accounted for poor visual acuity and nystagmus. Both cases had no syndromic associations. Spectacle correction was prescribed to both children, and low-vision aids and sun protection advised.

Conclusion

Oculocutaneous albinism (OCA) represents a range of inherited, congenital disorders of hypomelanosis, involving the skin, hair, and eyes with an estimated prevalence of 1 in 17,000 cases. Affected children suffer severe visual disability while early identification may potentially mitigate it, hence there is need to sensitize primary care practitioners regarding the general symptoms of OCA.

Mutations in the albinism gene oca2 alter vision-dependent prey capture behavior in the Mexican tetra

Understanding the phenotypic consequences of naturally occurring genetic changes, as well as their impact on fitness, is fundamental to understanding how organisms adapt to an environment. This is critical when genetic variants have pleiotropic effects, as determining how each phenotype impacted by a gene contributes to fitness is essential to understand how and why traits have evolved. Here, we characterized the effects of mutations in the oca2 gene, which underlie albinism and reductions of sleep in the blind Mexican cavefish Astyanax mexicanus, on larval prey capture. We found that when surface A. mexicanus with engineered mutations in oca2 are hunting, they use cave-like, wide-angle strikes to capture prey. However, unlike cavefish or surface fish in the dark, which utilize the lateral line when hunting, oca2 mutant (oca2Δ2bp/Δ2bp) surface fish can use vision when striking at prey from wide angles. We found that when raised under lighted conditions, pigmented surface fish outcompete albino oca2Δ2bp/Δ2bp surface fish when hunting in lighted conditions. In contrast, when surface fish are reared in darkness, oca2Δ2bp/Δ2bp surface fish outcompete their wild type siblings in the dark. This raises the possibility that albinism is detrimental to larval feeding in a surface-like lighted environment, but may confer an advantage to fish in cave-like, dark environments. Together, these results demonstrate that oca2 plays a role in larval feeding behavior in A. mexicanus, and expand our understanding of the pleiotropic phenotypic consequences of oca2 in cavefish evolution.

Arcuate pattern of retinal ganglion cell axons in oculocutaneous albinism has implications for axon pathfinding

Humans have a characteristic arcuate pattern of retinal ganglion cell (RGC) axons on the retina, indicating an unknown axon-repellent factor in the macula during development. This arcuate pattern has implications for diseases such as glaucoma. Albinism is an interesting group of conditions with loss of the radial foveal architecture (foveal hypoplasia) and abnormal RGC axon pathfinding at the optic chiasm. Here, we achieved optical coherence tomography imaging in a patient with oculocutaneous albinism type 1 (OCA1), which is challenging due to nystagmus. These scans showed a normal pattern of arcuate ganglion cells despite a severely hypoplastic fovea. This implies that there are multiple factors contributing to the radial pattern of the fovea and arcuate pattern of RGC axons, but OCA1 does not affect the latter.

Trichilemmal Carcinoma in a Patient With Oculocutaneous Albinism

Trichilemmal carcinoma (TC) is a rare adnexal neoplasm derived from the outer sheath of the hair follicle. Despite its aggressive histological features, TC typically exhibits low-grade clinical behavior, with local recurrences being more common than metastasis. This case report describes a 47-year-old Hispanic female with oculocutaneous albinism and a history of numerous nonmelanoma skin cancers (NMSCs) who presented with an erythematous papule on her forearm. Histopathology revealed TC characterized by basaloid keratinocytes with clear cytoplasm and peripheral palisading and a high proliferation rate confirmed by Ki-67. Surgical excision with 1.0 cm margins was performed, and final histopathology showed no residual tumor. Concurrently, the patient was diagnosed with metastatic squamous cell carcinoma (SCC) and started on pembrolizumab. This case highlights the increased susceptibility of individuals with oculocutaneous albinism to multiple and varied skin malignancies, stressing the need for vigilant skin surveillance and a broad differential diagnosis in this population. The patient's history underscores the importance of early detection and intervention to manage and mitigate the risk of advanced skin cancers.

The Impact of Oxytocin on Stimulus Discrimination of Zebrafish Albino and Non-Albino Models

Zebrafish have the ability, to a certain extent, to distinguish between different types of stimuli, including distinguishing between videos of conspecifics and non-conspecifics, a skill known as stimulus discrimination. In this study, we investigated the effects of oxytocin on this ability in albino and non-albino zebrafish models, focusing on the correlations between albinism, sensory deficiencies, and socio-emotional behaviors. Our hypothesis is based on the premise that oxytocin influences socio-emotional behaviors in zebrafish, with varying effects depending on phenotype (albino vs. non-albino), social context, and treatment duration. Studies have shown that albino zebrafish have more pronounced sensory deficiencies, meaning they may benefit more from oxytocin in terms of increased social comfort and interactions with conspecifics, while non-albino zebrafish would experience a reduction in defensive behaviors and anxiety. To test this, two experiments were conducted: one assessing the responses to video predator stimuli and the other comparing social interactions with real and video conspecifics. The results showed significant differences between the two groups: non-albino zebrafish exhibited stronger long-term reductions in anxiety-related behaviors, such as reaction speed and freezing, suggesting that oxytocin regulates defensive responses and aggression. Meanwhile, albino zebrafish showed greater improvements in social interactions, reflecting the nuanced, phenotype-dependent effects of oxytocin. These results not only confirm existing research but also highlight the therapeutic potential of oxytocin in treating socio-emotional deficiencies.

The importance of genetic counselling and testing in inherited eye diseases: A population-based retrospective study

PURPOSE

Inherited eye diseases (IEDs) are among the main causes of visual impairment and blindness in children and young people worldwide. The objective of our study was to characterize the prevalence and distribution of the most common IEDs and causative genes in our population.

STUDY DESIGN

Retrospective study based on medical records of patients with IEDs who underwent genetic counselling through our multidisciplinary low vision center from 2018 to 2020.

METHODS

Data retrieved from medical files included: year of consultation, age, gender, ethnicity, diagnosis, gene variants and mode of inheritance.

RESULTS

228 patients were included in our study. The most common diagnoses were inherited retinal diseases (IRDs) (41.2%) and albinism (32%). In 2018 and 2019 the number of patients reaching out for genetic counselling was between 50 and 60; this number doubled by 2020. The rate of pathogenic variant detection was 65.3%. The most common genes identified were TYR (29.2%), OCA2 (7.9%), ABCA4 (5.3%), TRPM1 (5.3%) and USH2A (4.4%).

CONCLUSION

Genetic counselling and testing became an essential part of caregiving for patients and families affected by these severe IEDs. The most common IEDs were IRDs in the Muslim population and albinism in the Jewish population. Pathogenic variants in the TYR gene were the most common in our cohort, OCA2 gene was the second in frequency, followed by ABCA4, TRPM1 and USH2A genes. We detected an increasing trend over the studied time in the number of patients reaching out for genetic counselling.

Oncogenic genodermatoses in paediatric patients with skin of colour: a review

Cutaneous neoplasms are relatively rare in children. Most commonly, skin cancers arise through environmental factors, particularly ultraviolet radiation; thus, age is the most predictive factor in developing cutaneous carcinomas. However, children born with certain genodermatoses are significantly more likely to develop malignancies and must be carefully monitored and treated. Most published data are based mainly on signs and symptoms present in White patients. Therefore, we aim to highlight the cutaneous presentations and relative differences of these genodermatoses among patients with skin of colour, who are underrepresented in medicine. We conducted a literature review of 504 patients presented in 236 published articles. Manuscripts with accessible case reports for children aged ≤ 17 years were included. Patients with skin of colour often present with fewer classical findings and have higher incidences of scarring and dyspigmentation. There is also a higher incidence of consanguinity in affected patients. Providers who are able to recognize nonclassical signs can provide proper management and treatment regimens, potentially bringing outcomes for patients with skin of colour more in line with those of White children.

A Recessive oca2 Mutation Underlies Albinism in Xiphophorus fish

Oculocutaneous albinism (OCA) is a group of genetic disorders characterized by impaired melanin production, leading to reduced pigmentation in the skin, hair, and eyes. Xiphophorus , a genus of small freshwater fish, has been a pivotal model organism in pigmentation disorder research, providing key findings in the genetic pathways governing physiological and pathological pigment cell biology. Leveraging the well-established research framework provided by Xiphophorus , we have identified a spontaneously occurring albinism phenotype in swordtail fish Xiphophorus hellerii . Genetic mapping of albino fish showed that albinism is associated with a recessive mutation in the oca2 gene. This discovery provides a novel opportunity to explore functions of oca2 gene in pigment cell differentiation, pigment synthesis, melanosome assembly and transportation function and amelanotic melanoma development.

Advancing Insights into Pediatric Macular Diseases: A Comprehensive Review

Pediatric macular disorders are a diverse group of inherited retinal diseases characterized by central vision loss due to dysfunction and degeneration of the macula, the region of the retina responsible for high-acuity vision. Common disorders in this category include Stargardt disease, Best vitelliform macular dystrophy, and X-linked retinoschisis. These conditions often manifest during childhood or adolescence, with symptoms such as progressive central vision loss, photophobia, and difficulty with fine visual tasks. Underlying mechanisms involve genetic mutations that disrupt photoreceptor and retinal pigment epithelium function, accumulating toxic byproducts, impaired ion channel activity, or structural degeneration. Advances in imaging modalities like optical coherence tomography and fundus autofluorescence have improved diagnostic accuracy and disease monitoring. Emerging therapies are transforming the treatment landscape. Gene therapy and genome editing hold promise for addressing the genetic basis of these disorders, while stem cell-based approaches and pharmacological interventions aim to restore retinal function and mitigate damage. Personalized medicine, driven by genomic sequencing, offers the potential for tailored interventions. Despite current challenges, ongoing research into molecular mechanisms, advanced imaging, and innovative therapies provides hope for improving outcomes and quality of life in children with macular disorders.

The degradation of TYR variants derived from Chinese OCA families is mediated by the ERAD and ERLAD pathway

Oculocutaneous albinism (OCA) is a genetically heterogeneous group of autosomal recessive disorders, which presents with decreased or absent pigmentation in the hair, skin, and eyes. OCA1, as a subtype of OCA, is caused by mutations in the tyrosinase gene (TYR). In this study, we performed in vitro functional analysis of eight TYR variants (one frameshift variant: c.929dupC (p.Arg311Lysfs*7); seven missense variants: c.896G>A (p.Arg299His), c.1234C>A (p.Pro412Thr), c.1169A>G (p.His390Arg), c.937C>A (p.Pro313Thr), c.636A>T (p.Arg212Ser), c.623 T>G (p.Leu208Arg), c.1325C>A (p.Ser442Tyr)) identified in Chinese OCA families. TYR plasmids were transfected into HEK 293 T cells to explore the effects of TYR variants on their processing, protein expression, activity, and degradation. The results showed that all eight variants caused TYR to be retained in the endoplasmic reticulum (ER), processing was blocked, and TYR activity almost disappeared; the frameshift variant caused the size of the TYR protein to be reduced by about 30KD, and the protein expression of the remaining seven missense variants was reduced; the ER-associated degradation (ERAD) pathway mediates the degradation of TYR variants that occur on the Tyrosinase copper-binding domain, while the degradation of TYR variants that are not located on that domain may be mediated by a new degradation pathway--ER-to-lysosome-associated degradation (ERLAD). In summary, TYR variants affected their protein processing and activity, and may also induce ER stress and trigger degradation through the ERLAD pathway in addition to the ERAD degradation pathway, providing new insights into the potential pathogenic mechanism for OCA1 caused by TYR variants.

Curation of OCA2 Variants of Uncertain Significance From Chinese Oculocutaneous Albinism Patients Based on Multiplex Assays

Oculocutaneous albinism type 2 (OCA-2, OMIM: 203200) is associated with variants in the OCA2 gene. In this study, we aimed to re-classify variants of uncertain significance (VUS) in OCA2 by evaluating subcellular localization and channel activity through multiplex assays of variant effect (MAVEs). Following the ClinGen guidelines for PS3 evidence, we selected 13 OCA2 variants from ClinVar (6 benign/likely benign [B/LB] and 7 pathogenic/likely pathogenic [P/LP]) for OddsPath analysis. The P/LP variants exhibited abnormal functions, while the B/LB variants demonstrated normal functions, supporting the application of "PS3_moderate" evidence for VUS re-classification. In our functional evaluation of 30 VUS identified in 38 individuals with suspected OCA-2 by trio whole-exome sequencing, we observed 6 VUS with abnormal localization and 11 with abnormal channel activity. Based on PS3_moderate evidence, 8 VUS were re-classified as LP, while 22 remained VUS. Consequently, 7 out of 38 previously undiagnosed patients received a molecular diagnosis of OCA-2. These MAVEs offer a robust approach for curating OCA2 VUS, enhancing diagnostic accuracy, and informing genetic counseling. Additionally, this variant cohort is a valuable resource for public databases.

Genotypic and phenotypic analysis of an oculocutaneous albinism patient: a case report and review of the literature

BACKGROUND

Oculocutaneous albinism is a rare autosomal recessive disorder caused by congenital melanin deficiency, resulting in hypopigmentation of the eyes, hair, and skin. This study included a Chinese family with an oculocutaneous albinism pedigree, in which the proband presented with oculocutaneous albinismcombined with secondary angle closure, which has been rarely reported in previous literature. This article primarily focused on the clinical and genetic examination results of this patient and provided recommendations for ophthalmologist to treat patients with oculocutaneous albinism in clinical practice.

CASE PRESENTATION

The proband in this case study is a 53-year-old Chinese male who showed depigmentation of the skin, hair, iris, and fundus, accompanied by photophobia, decreased vision, high intraocular pressure, nystagmus, macular fovea hypoplasia, and cataracts. Owing to the opacity and expansion of the lens, the volume ratio of lens to eyeball was increased, causing crowded anterior segment, bombed iris, and narrowed chamber angle and, ultimately, leading to secondary angle closure. Whole-exome sequencing suggested that the two patients in the pedigree harbored the compound heterozygous variants c.230G > A (p. Arg77Gln) and c.832G > A (p. Arg278*) in the TYR gene, while the healthy member carried the TYR c.230G > A (p. Arg77Gln) variant, which was consistent with the autosomal recessive inheritance pattern and further confirmed the diagnosis was oculocutaneous albinism. On the basis of the above results, the patient was diagnosed with oculocutaneous albinism, senile mature cataract, and secondary angle closure in the right eye and ocular hypertension in the left eye, as well as bilateral nystagmus. Then, the patient was prescribed carteolol eye drops to control intraocular pressure and underwent phacoemulsification and intraocular lens implantation surgery for the right eye. Postoperatively, the patient's intraocular pressure was effectively controlled, and visual acuity improved.

CONCLUSION

We report a patient with oculocutaneous albinism combined with cataract and secondary angle closure, and whole-exome sequencing suggested that he harbored TYR gene variants. Comprehensive examinations were important for identifying the causes of angle closure and making proper treatment strategies. Genetic testing enabled precise diagnosis and genetic counseling.

Early diagnosis of immunodeficient patients with partial albinism: The role of hair study and peripheral blood smear

BACKGROUND

Primary immunodeficiency diseases (inborn errors of immunity) with partial albinism are a group of autosomal recessive syndromes including Chediak Higashi Syndrome (CHS), Griscelli Syndrome type 2 (GS2), Hermansky-Pudlak Syndromes type 2 and 10 (HPS2, HPS10), Vici syndrome and P14/LAMTOR2 deficiency.

METHODS

Twenty-five patients including 10 CHS, 10 GS2, and 5 HPS2 were evaluated in this study within the last 10 years. Five cases with oculocutaneous albinism (OCA) and 5 healthy subjects without albinism were used as two control groups. Genetic analyses were performed by whole exome or panel sequencing or targeted Sanger sequencing. Subsequently, leukocyte granules in peripheral blood smear and hair shaft were examined as screening tests.

RESULTS

Giant granules were only presented in the leukocytes cytoplasm of 10/10 CHS patients. The uneven cluster of pigments and giant melanin granules in hair samples were observed in 10/10 GS2 and 10/10 CHS patients, respectively. In both 5/5 OCA and 5/5 HPS2 patients, there were regular pigments in the middle of hair shafts. Genetic analyses were performed for all patients, revealing 7 novel variants in LYST gene for CHS patients and 4 novel variants in AP3B1 for HPS2 patients.

CONCLUSION

Receiving hematopoietic stem cell transplantation (HSCT) in a timely manner is crucial in CHS and GS2 patients; therefore, screening tests may provide a vital clue for early diagnosis in these patients. However, the final confirmation of CHS, GS2, and HPS2 disorders is done by genetic assay.

Transcriptome-based screening and validation of key genes for wool color in cashmere goats

BACKGROUND

Colored wool from cashmere goats is increasingly popular among consumers, but the transcriptomic differences between coat colors are poorly understood.

OBJECTIVES

This study aimed to screen for coat color regulation-associated genes in cashmere goats to ascertain their underlying molecular mechanisms.

METHODS

Transcriptomic sequencing of skin tissues from black (BC), brown (YC), and white cashmere (WC) goats was performed. Immunohistochemistry and western blotting were used to validate SLC24A4 and DCT expression, two essential genes identified for coat color determination.

RESULTS

We identified 6,518 differentially expressed genes (DEGs) in the BC vs. WC group (3,919 upregulated, 2,599 downregulated). Next, 5,593 DEGs were identified in the YC vs. WC group (3,629 upregulated, 1,964 downregulated). Finally, 4,538 DEGs were expressed in both groups, with 1,980 and 1,055 DEGs exclusively expressed in either group. Functions and pathways associated with hair color were enriched, including melanosomes, melanocyte migration, melanin biosynthesis processes and functions, and melanogenesis pathways. TYRP1, SLC24A4, PMEL, OCA2, and DCT were significantly upregulated in BC goat skin, while ASIP was significantly upregulated in YC skin. Additionally, KIT, POMC, SLC24A5, Wnt3a, and EDN3 were DEGs for different coat colors. Immunohistochemistry revealed SLC24A4 and DCT expression in dermal papillae, inner and outer root sheaths, and the hair follicle matrix. Western blotting showed that SLC24A4 protein levels were highest in BC goat skin. DCT protein levels were also highest in BC goat skin, albeit not significantly.

CONCLUSION

These results further our understanding of coat color regulation in cashmere goats, establishing a foundation for their molecular breeding.

Common Variants in the TYR Gene with Unclear Pathogenicity as the Cause of Oculocutaneous Albinism in a Cohort of Russian Patients

Background: oculocutaneous albinism (OCA) is a hereditary impairment of skin, hair, and eye pigmentation. The most common form of albinism is autosomal recessive albinism, caused by mutations in the TYR gene, accounting for approximately 40-50% of all cases of the disease in European populations. Common hypomorphic variants in the TYR gene could lead to a mild form of albinism in a compound heterozygous state with a pathogenic variant. Methods: we examined by allele specific MLPA a cohort consisting of 118 unrelated patients with albinism and 10 parents of these patients. The control cohort consisted of 200 unexamined Russian residents. Results: the patients with albinism were divided into three groups: without pathogenic variants in the TYR gene-70 patients, with one pathogenic variant in the TYR gene-20 patients, and with two pathogenic variants in the TYR gene-28 patients. Among the 20 patients with a single heterozygous variant in the TYR gene, 15 patients had the c.575C>A p.(Ser192Tyr) variant, and 15 had the c.1205G>A p.(Arg402Gln) variant. Both the c.575C>A p.(Ser192Tyr) and c.1205G>A p.(Arg402Gln) variants were identified in 12 patients. In addition to the aforementioned variants, an intronic variant c.1185-6208A>G (rs147546939) was identified in seven patients. Conclusions: the frequencies and the number of alleles c.575A, c.1205A, and c.1185-6208G in different groups of patients and the control group were compared. In this study, we demonstrate that the complex alleles [c.575C>A p.(Ser192Tyr); c.1205G>A p.(Arg402Gln)] and [c.575C>A p.(Ser192Tyr); c.1185-6208A>G; c.1205G>A p.(Arg402Gln)] are associated with oculocutaneous albinism, which is consistent with findings from other researchers.

Albinism and Blood Cell Profile: The Peculiar Case of Asinara Donkeys

The complete blood cell count (CBC) was screened in a group of 15 donkeys, of which 8 were of Asinara breed (oculocutaneous albinism type 1, OCA1) and 7 of Sardo breed (gray coat). All donkeys were kept under same management and dietary conditions and underwent periodic health monitoring in the month of June 2024, at the peak of the positive photoperiod, at Mediterranean latitudes. One aliquot of whole blood, drawn from each individual into K2-EDTA containing tubes, was analyzed for the complete blood cell count through an automatic analyzer, within two hours of sampling. Data were analyzed and compared by one-way ANOVA, where the breed was an independent variable. All animals appeared clinically healthy, though mild eosinophilia was observed in Sardo donkeys. The red blood cell line showed peculiar traits for Asinara donkeys, which displayed significantly higher circulating red blood cell numbers than gray coat Sardo donkeys (RBC, 5.19 vs. 3.80 1012/mL ± 0.98 pooled-St. Dev, respectively; p = 0.017). RBCs also exhibited a smaller diameter and higher degree of anisocytosis in Asinara donkeys, along with lower hematocrit value, albeit within physiological ranges. Taken all together, such hematological profile depicts a peculiar trait of the red blood cell line in albino donkeys during the positive photoperiod.

A novel deletion in the BLOC1S6 Gene Associated with Hermansky-Pudlak syndrome type 9 (HPS-9)

BACKGROUND

Hermansky-Pudlak Syndrome (HPS), a rare autosomal recessive disorder, is characterized by oculocutaneous albinism, bleeding diathesis, and sometimes severe lung problems and inflammatory bowel disease. Symptoms include skin and hair pigmentation variations, along with visual impairments. Variants in eleven genes encoding protein complexes essential for membrane trafficking and intracellular endosomal transport pathways underlie various recognized HPS subtypes. This study focuses on HPS-9, a subtype of Hermansky-Pudlak Syndrome caused by a variant in the BLOC1S6 gene, which is a subunit of the BLOC1 complex. In this study, a novel Copy Number Variation (CNV) in the aforementioned gene in an Iranian family is reported. The study aims to better understand the etiology of HPS-9 symptoms by identifying and confirming the variant and determining whether the gene is expressed despite the deletion. There have only been five reports of this syndrome in the literature thus far. Our novel CNV represents a significant contribution to understanding the genetic basis of HPS-9.

RESULTS

This study investigates a male patient presenting with albinism. Whole Exome Sequencing (WES) identified a homozygous deletion of approximately 350 bp using CNV analysis. The deletion affects the intronic region of the BLOC1S6 gene, causing uncertainties in defining the exact boundaries due to WES limitations. Primer walking and GAP-PCR techniques were used to define the deletion boundaries. Subsequent assessments of this variant across other family members helped identify homozygous affected members and heterozygous carriers. The absence of BLOC1S6 expression in the affected individual was confirmed through Real-time PCR experiments. These findings underscore the importance of understanding the implications for the patient's healthcare and potential therapeutic approaches.

CONCLUSION

This study introduces a case of Hermansky-Pudlak Syndrome Type 9 (HPS-9) caused by a homozygous deletion in the BLOC1S6 gene. We identified an approximately 7-kb deletion encompassing exon 1 and the intronic region of the gene. The absence of BLOC1S6 expression, confirmed via Real-time PCR, highlights the importance of studying the pathogenicity of the deletion and its impact on the patient's health. Our findings contribute to the sparse knowledge on HPS-9 and underscore the need for further exploration into the genetic causes of this rare disorder.

Genotype-Phenotype Correlation Model for the Spectrum of TYR-Associated Albinism

We present two children aged 3 and 5 years who share identical TYR genotype, yet exhibit contrasting phenotypic manifestations in terms of eye, skin, and hair coloration. The patients are heterozygous for TYR c.1A>G, p. (Met1?), which is pathogenic, and homozygous for TYR c.1205G>A, p. (Arg402Gln), which is classified as a risk factor. The children manifested diminished visual acuity, nystagmus, and foveal hypoplasia. The first patient presented with hypopigmentation of the skin, hair, and ocular tissues, while the second patient presented with hypopigmentation of the skin, hair, retinal pigment epithelium, and choroid with dark brown irises. Furthermore, the brown-eyed subject presented astigmatic refractive error and both global and local stereopsis capabilities, contrasting with the presentation of hypermetropia, strabismus, and the absence of stereopsis in the blue-eyed individual. Herein, we propose a genotype-phenotype correlation model to elucidate the diverse clinical presentations stemming from biallelic and triallelic pathogenic variants in TYR, establishing a link between the residual tyrosinase activity and resultant phenotypes. According to our proposed model, the severity of TYR variants correlates with distinct albino phenotypes. Our findings propose the potential association between reduced pigmentation levels in ocular tissues and binocular functions, suggesting pigmentation as a possible independent variable influencing the onset of strabismus-an association unreported until now in the existing literature.

Mutations in the albinism gene oca2 alter vision-dependent prey capture behavior in the Mexican tetra

Understanding the phenotypic consequences of naturally occurring genetic changes, as well as their impact on fitness, is fundamental to understanding how organisms adapt to an environment. This is critical when genetic variants have pleiotropic effects, as determining how each phenotype impacted by a gene contributes to fitness is essential to understand how and why traits have evolved. A striking example of a pleiotropic gene contributing to trait evolution is the oca2 gene, coding mutations in which underlie albinism and reductions of sleep in the blind Mexican cavefish, Astyanax mexicanus. Here, we characterize the effects of mutations in the oca2 gene on larval prey capture. We find that when conspecific surface fish with engineered mutations in the oca2 allele are hunting, they use cave-like, wide angle strikes to capture prey. However, unlike cavefish or surface fish in the dark, which rely on lateral line mediated hunting, oca2 mutant surface fish use vision when striking at prey from wide angles. Finally, we find that while oca2 mutant surface fish do not outcompete pigmented surface siblings in the dark, pigmented fish outcompete albino fish in the light. This raises the possibility that albinism is detrimental to larval feeding in a surface-like lighted environment, but does not have negative consequences for fish in cave-like, dark environments. Together, these results demonstrate that oca2 plays a role in larval feeding behavior in A. mexicanus. Further, they expand our understanding of the pleiotropic phenotypic consequences of oca2 in cavefish evolution.

Genetic Linkage between CAPN5 and TYR Variants in the Context of Albinism and Autosomal Dominant Neovascular Inflammatory Vitreoretinopathy Absence: A Case Report

We present a case involving a patient whose clinical phenotype aligns with oculocutaneous albinism (OCA), yet exhibits a complex genotype primarily characterized by variants of unknown significance (VUS). An 11-year-old boy manifested iris hypopigmentation and translucency, pronounced photophobia, diminished visual acuity and stereopsis, nystagmus, reduced pigmentation of the retina, and foveal hypoplasia. Genetic testing was performed. A heterozygous missense VUS CAPN5 c.230A>G, p.(Gln77Arg), a heterozygous missense VUS TYR c.1307G>C, p.(Gly436Ala), and a heterozygous missense variant TYR c.1205G>A, p.(Arg402Gln) which was classified as a risk factor, were identified. We hypothesized that the TYR c.1307G>C, p.(Gly436Ala) variant is in genetic disequilibrium with the TYR c.1205G>A, p.(Arg402Gln) variant leading to deficient expression of melanogenic enzymes in retinal cells, resulting in the manifestation of mild OCA. Additionally, this study represents the case where we did not detect chiasmal misrouting in visual evoked potentials, nor did we observe a shift in the distribution of ganglion cell thickness from a temporal to a central position. Moreover, our patient's case supports the probable benign nature of the CAPN5 c.230A>G, p.(Gln77Arg) variant.

Successful treatment of retinopathy of prematurity in oculocutaneous albinism with OCA2 variants: a case report and review of literature

BACKGROUND

Oculocutaneous albinism (OCA) is a group of autosomal recessive hereditary disorders that affect melanin biosynthesis, resulting in abnormalities in hair, skin, and eyes. Retinopathy of prematurity (ROP) is a proliferative retinopathy mainly observed in premature infants with low birth weight and early gestational age, but it can also affect full-term infants or children with normal weight, particularly in developing countries. The coexistence of ROP and OCA is rare. There is limited documentation regarding treatment approaches, with few studies reporting positive outcomes with laser treatment due to the absence of melanin pigment. This study discusses the treatment challenges in a female infant diagnosed with ROP and OCA, and underscores the importance of genetic analysis in guiding therapeutic decisions for this rare comorbid condition.

CASE PRESENTATION

The study presents a case of ROP occurring concurrently with OCA. Genetic testing revealed two variants, c.727C > T (p.R243C) and c.1832 T > C (p.L611P), in the OCA2 gene, inherited from the patient's mother and father, respectively. The identified mutations were consistent with a diagnosis of OCA2, classified as a subtype of OCA. The patient initially received intravitreal anti-vascular endothelial growth factor (anti-VEGF) injection, followed by laser photocoagulation therapy for a recurrent event. A favorable outcome was observed during the 2-month follow-up period.

CONCLUSIONS

The co-occurrence of ROP and OCA is a rare phenomenon, and this is the first recorded case in the Chinese population. The current case supports the use of laser as the primary treatment modality for ROP in OCA2 patients with partial pigmentation impairment. Furthermore, genetic analysis can aid in predicting the effectiveness of laser photocoagulation in this patient population.

Nystagmus and Foveal Hypoplasia in a Carrier of Oculocutaneous Albinism

We report a 23-year-old female patient with ophthalmic features of albinism, including refractive errors, nystagmus, depigmented fundus, and foveal hypoplasia. She presented for a rhegmatogenous retinal detachment, which was surgically reattached with no complications. Further genetic testing revealed the presence of a heterozygous pathogenic oculocutaneous albinism OCA2 gene mutation, conferring carrier status. To the best of our knowledge, this is the first reported case of typical ocular phenotype of albinism, specifically nystagmus, in a patient who is carrier for oculo-cutaneous albinism. Further research is required to expand the genotype-phenotype relationship in carriers of oculocutaneous albinism. [Ophthalmic Surg Lasers Imaging Retina 2024;55:349-353.].

A patient with albinism and retinitis pigmentosa, a case report

Purpose

To present a case of molecularly confirmed oculocutaneous albinism (OCA) and retinitis pigmentosa (RP).

Observations

A 46-year-old male with a lifelong established diagnosis of OCA and baseline best corrected visual acuity (BCVA) of 20/200, presented for worsening visual acuity over the last few years. BCVA was light perception and hand motion at face for the right and left eye, respectively. Fundus exam showed hypopigmented fundi with visible choroidal vessels and blunted foveal reflexes in both eyes. Optical coherence tomography showed foveal hypoplasia and outer retinal degenerative changes not typical of OCA. Fundus autofluorescence (FAF) imaging showed focal areas of decreased signal at the fovea, similar to areas of atrophy in an age matched patient with PDE6A-RP. Genetic testing identified a homozygous disease-causing variant in TYR c.1467dup, p. (Ala490Cysfs*20) causing OCA, and a homozygous pathogenic variant c.304C > A, p. (Arg102Ser) in PDE6A causing autosomal recessive RP.

Conclusions and importance

This is the first report of a patient with OCA and RP. The lack of pigmentary changes can make the diagnosis of RP challenging in patients with albinism. FAF can show features suggestive of RP and genetic testing can establish the diagnosis. The findings described herein may help physicians diagnose an extremely rare phenotype.

Whole-genome resequencing reveals genetic diversity, differentiation, and selection signatures of yak breeds/populations in southwestern China

The Sichuan-Yunnan region is the main production area of yaks in southwestern China, with rich genetic resources of Yaks. Nevertheless, there have been limited study on the genetic characteristics of the entire yak populations in Tibet and southwestern China. In this study, we performed whole-genome resequencing to identify genetic variation information in a total of 198 individuals from six yak breeds (populations) in Sichuan (Muli yak, Jinchuan yak, Changtai yak, Maiwa yak), Yunnan (Zhongdian yak), and Tibet (Tibetan yak). The aim was to investigate the whole-genome genetic diversity, population genetic structure, and genome selection signatures. We observed that all six populations exhibit abundant genetic diversity. Except for Tibetan yaks, which showed low nucleotide diversity (0.00104), the remaining yak populations generally displayed high nucleotide diversity (0.00129-0.00153). Population genetic structure analysis revealed that, among the six yak populations, Muli yak exhibited greater differentiation from other yak populations and formed a distinct cluster independently. The Maiwa yak population displayed a complex genetic structure and exhibited gene exchange with Jinchuan and Changtai yaks. Positive selection signals were detected in candidate genes associated with growth (GNB4, HMGA2, TRPS1, and LTBP1), reproduction (PI4KB, DYNC1I1, and GRIP1), immunity (CD200 and IL1RAP), lactation (SNX13 and CPM), hypoxia adaptation (NDUFB6, PRKN, and MRPS9), hair (KRT24, KRT25, and KRT26), meat quality (SUCLG2), digestion and absorption (CLDN1), and pigment deposition (OCA2) using the integrated Pi and F ST methods. This study provides significant insights into understanding the whole-genome genetic characteristics of yak populations in Tibet and southwestern China.

The prevalence of autism among children with albinism

BACKGROUND

The association between Autism spectrum disorders (ASD) and visual impairment has been mentioned in the literature. The aim of our study was to investigate the prevalence of autism among children with albinism compared to the prevalence of ASD in children with visual impairment secondary to other causes.

METHODS

Retrospective study of children with albinism from January 2015 to December 2020. A control group was created with children with early onset visual impairment of similar visual range and age, secondary to diagnosis other than albinism. Patients with associated Autism were identified in both groups.

RESULTS

Seven hundred and eight children aged 1-18 years with visual impairment were included in the study. 401 children had a diagnosis of albinism, of whom 14 were also diagnosed with ASD. In the control group, composed of 307 patients, only 3 had ASD (p: 0·03).

CONCLUSIONS

The prevalence of ASD in patients with albinism was 1 in 28, while in children with visual impairment from other causes was 1 in 102. We aim to raise awareness of the higher prevalence of autism in children diagnosed with albinism in order to reach earlier diagnosis and support.

UVR and RPE - The Good, the Bad and the degenerate Macula

Ultraviolet Radiation (UVR) has a well-established causative influence within the aetiology of conditions of the skin and the anterior segment of the eye. However, a grounded assessment of the role of UVR within conditions of the retina has been hampered by a historical lack of quantitative, and spectrally resolved, assessment of how UVR impacts upon the retina in terms congruent with contemporary theories of ageing. In this review, we sought to summarise the key findings of research investigating the connection between UVR exposure in retinal cytopathology while identifying necessary avenues for future research which can deliver a deeper understanding of UVR's place within the retinal risk landscape.

Hypomorphic variants in inherited retinal and ocular diseases: A review of the literature with clinical cases

Hypomorphic variants decrease, but do not eliminate, gene function via a reduction in the amount of mRNA or protein product produced by a gene or by production of a gene product with reduced function. Many hypomorphic variants have been implicated in inherited retinal diseases (IRDs) and other genetic ocular conditions; however, there is heterogeneity in the use of the term "hypomorphic" in the scientific literature. We searched for all hypomorphic variants reported to cause IRDs and ocular disorders. We also discuss the presence of hypomorphic variants in the patient population of our ocular genetics department over the past decade. We propose that standardized criteria should be adopted for use of the term "hypomorphic" to describe gene variants to improve genetic counseling and patient care outcomes.

A Novel Type of Autosomal Dominant Episodic Nystagmus Segregating with a Variant in the FRMD5 Gene

To describe the phenotype of a novel form of autosomal dominant episodic nystagmus and to identify the potential genetic aetiology. We identified several individuals in a large Swedish family affected by episodic nystagmus. In total, 39 family members from five generations were invited to participate in the study, of which 17 were included (12 affected and 5 unaffected). The phenotype of the nystagmus was described based on data collected from family members through questionnaires, interviews, clinical examinations and from video recordings of ongoing episodes of nystagmus. Whole genome sequencing (WGS) and further Sanger sequencing for segregation of the identified candidate variants was performed in eight participants (six affected and two unaffected). The 12 affected participants showed a phenotype with episodic nystagmus of early onset. A vertical jerk nystagmus with variable amplitude and frequency was characterized in the analysed video material. No other eye pathology or other disease that could explain the episodic nystagmus was identified among the family participants. Genetic analysis identified a missense variant (p.Ser375Phe) in the gene FRMD5, which segregated with the disease in the eight individuals analysed, from three generations. We describe a novel autosomal dominant form of early onset episodic nystagmus and suggest the FRMD5 gene as a strong candidate gene for this disorder.

What Have We Learned about the Prevention of NMSC from Albino Patients from Malawi? Secondary Prevention Maintained over Time

BACKGROUND

We have conducted cooperative campaigns focusing on albino patients in a rural area of Malawi. What have we learned?

METHODS

Three surgical campaigns were performed in Nkhotakota district (2019-2023). Albino clinical and tumor characteristics were collected.

RESULTS

Between 22 and 75 albinos were evaluated in each campaign (mean age < 28 years old). Most patients did not use sunscreen in a way that provided optimal photoprotection. Regarding tumors, the proportion of basal and squamous cell carcinomas ranged from 1:1 to almost 2:1. Of 156 albino patients, 34 attended more than once. However, of the 19 patients with 30 tumors operated on in 2021, only seven were assessed the following year (12 were lost to follow-up). At least 14 albinos with locally advanced tumors were evaluated.

CONCLUSIONS

Distributing photoprotective clothing could be more efficient or perhaps an earlier measure of sunscreen in rural Africa as it does not require permanent repositioning. Very-high-risk patients (previous interventions with positive margins or high-risk tumors, intense actinic damage, and new tumors constantly appearing, especially those presenting SCCs) require close follow-up and treatment and represent our main target. Secondary prevention with Malawian collaboration and the use of teledermatology is essential for patient tracking, as they are able to offer curative treatments.

Melanocytes in regenerative medicine applications and disease modeling

Melanocytes are dendritic cells localized in skin, eyes, hair follicles, ears, heart and central nervous system. They are characterized by the presence of melanosomes enriched in melanin which are responsible for skin, eye and hair pigmentation. They also have different functions in photoprotection, immunity and sound perception. Melanocyte dysfunction can cause pigmentary disorders, hearing and vision impairments or increased cancer susceptibility. This review focuses on the role of melanocytes in homeostasis and disease, before discussing their potential in regenerative medicine applications, such as for disease modeling, drug testing or therapy development using stem cell technologies, tissue engineering and extracellular vesicles.

Crowding under scotopic and photopic vision in albino and normal-sighted participants

Crowding is a phenomenon in which the ability to recognize an object in a clutter deteriorates. It is, therefore, a fundamental aspect of object recognition and crucial in deciphering resolution. For visually impaired individuals, deficiency in crowding has a tremendous effect on vision and may reflect and predict the amount of deterioration in vision. It is well established that albinos suffer much more from crowding than normally sighted individuals under daylight luminance conditions. However, to our knowledge, this study is the first to investigate crowding in albino participants under low light conditions. In this study, we explored the crowding effect in a group of albino participants (n = 9) and a control group of normally sighted participants (n = 9). Crowding was conducted under daylight (photopic vision) and low light (scotopic vision). We measured the visual acuity threshold under crowding in three-letter spacing (0.5, 1, and 1.5) and compared it to a single target. Results indicate that albino participants experienced stronger crowding than the control under the photopic condition, while crowding under the scotopic condition was apparent in the albino but abolished for the control group. These findings highlight the importance of considering luminance when discussing the visually impaired population in general. In particular, it suggests that crowding in albinism is based on a peripheral-like mechanism and may indicate a cessation in visual development.

In Vivo Assessment of Retinal Phenotypes in Axenfeld-Rieger Syndrome

Purpose

Axenfeld-Rieger syndrome (ARS) is characterized by ocular anomalies including posterior embryotoxon, iridocorneal adhesions, corectopia/iris hypoplasia, and developmental glaucoma. Although anterior segment defects and glaucoma contribute to decreased visual acuity, the role of potential posterior segment abnormalities has not been explored. We used high-resolution retinal imaging to test the hypothesis that individuals with ARS have posterior segment pathology.

Methods

Three individuals with FOXC1-ARS and 10 with PITX2-ARS completed slit-lamp and fundus photography, optical coherence tomography (OCT), OCT angiography, and adaptive optics scanning light ophthalmoscopy (AOSLO). Quantitative metrics were compared to previously published values for individuals with normal vision.

Results

All individuals demonstrated typical anterior segment phenotypes. Average ganglion cell and inner plexiform layer thickness was lower in PITX2-ARS, consistent with the glaucoma history in this group. A novel phenotype of foveal hypoplasia was noted in 40% of individuals with PITX2-ARS (but none with FOXC1-ARS). Moreover, the depth and volume of the foveal pit were significantly lower in PITX2-ARS compared to normal controls, even excluding individuals with foveal hypoplasia. Analysis of known foveal hypoplasia genes failed to identify an alternative explanation. Foveal cone density was decreased in one individual with foveal hypoplasia and normal in six without foveal hypoplasia. Two individuals (one from each group) demonstrated non-foveal retinal irregularities with regions of photoreceptor anomalies on OCT and AOSLO.

Conclusions

These findings implicate PITX2 in the development of the posterior segment, particularly the fovea, in humans. The identified posterior segment phenotypes may contribute to visual acuity deficits in individuals with PITX2-ARS.

Identification of Candidate Genes for Red-Eyed (Albinism) Domestic Guppies Using Genomic and Transcriptomic Analyses

Guppies are small tropical fish with brightly colored bodies and variable tail shapes. There are two phenotypes of domestic guppy eye color: red and black. The wild type is black-eyed. The main object of this study was to identify candidate genes for the red-eyed phenotype in domestic guppies. We hope to provide molecular genetic information for the development of new domestic guppy strains. Additionally, the results also contribute to basic research concerning guppies. In this study, 121 domestic guppies were used for genomic analysis (GWAS), and 44 genes were identified. Furthermore, 21 domestic guppies were used for transcriptomic analysis, and 874 differentially expressed genes (DEGs) were identified, including 357 upregulated and 517 downregulated genes. Through GO and KEGG enrichment, we identified some important terms or pathways mainly related to melanin biosynthesis and ion transport. qRT-PCR was also performed to verify the differential expression levels of four important candidate genes (TYR, OCA2, SLC45A2, and SLC24A5) between red-eyed and black-eyed guppies. Based on the results of genomic and transcriptomic analyses, we propose that OCA2 is the most important candidate gene for the red-eyed phenotype in guppies.

Genetic analysis of albinism caused by compound heterozygous mutations of the OCA2 gene in a Chinese family

BACKGROUND

Oculocutaneous albinism (OCA) is a group of rare genetic disorders characterized by a reduced or complete lack of melanin in the skin, hair, and eyes. Patients present with colorless retina, pale pink iris, and pupil, and fear of light. The skin, eyebrows, hair, and other body hair are white or yellowish-white. These conditions are caused by mutations in specific genes necessary for the production of melanin. OCA is divided into eight clinical types (OCA1-8), each with different clinical phenotypes and potential genetic factors. This study aimed to identify the genetic causes of non-syndromic OCA in a Chinese Han family.

METHODS

We performed a comprehensive clinical examination of family members, screened for mutation loci using whole exome sequencing (WES) technology, and predicted mutations using In silico tools.

RESULTS

The patient's clinical manifestations were white skin, yellow hair, a few freckles on the cheeks and bridge of the nose, decreased vision, blue iris, poorly defined optic disk borders, pigmentation of the fundus being insufficient, and significant vascular exposure. The WES test results indicate that the patient has compound heterozygous mutations in the OCA2 gene (c.1258G > A (p.G420R), c.1441G > A (p.A481T), and c.2267-2 A > C), respectively, originating from her parents. Among them, c.1258G > A (p.G420R) is a de novo mutation with pathogenic. Our analysis suggests that compound heterozygous mutations in the OCA2 gene are the primary cause of the disease in this patient.

CONCLUSIONS

The widespread application of next-generation sequencing technologies such as WES in clinical practice can effectively replace conventional detection methods and assist in the diagnosis of clinical diseases more quickly and accurately. The newly discovered c.1258G > A (p.G420R) mutation can update and expand the gene mutation spectrum of OCA2-type albinism.

Unveiling genetics of non-syndromic albinism using whole exome sequencing: A comprehensive study of TYR, TYRP1, OCA2 and MC1R genes in 17 families

BACKGROUND

Oculocutaneous albinism (OCA) is a group of skin depigmentation disorders. Clinical presentation of OCA includes defects in melanocyte differentiation, melanin biosynthesis, and melanosome maturation and transport.

OBJECTIVES

A molecular diagnostics study of families presenting oculocutaneous albinism.

METHODS

In this study, 17 consanguineous OCA families consisting of 93 patients were investigated. Whole Exome Sequencing (WES) of the index patient in each family were performed. Short listed variants of WES were Sanger validated for Mendelian segregation in obligate carriers and other available family members. Variant prioritization and pathogenicity were classified as per the criteria of American College Medical Genetics and Genomics (ACMG). Comparative computational modelling was performed to predict the potential damaging effect of the altered proteins.

RESULTS

15 pathogenic variations: c.132 T > A, c.346C > T, c.488C > G, c.1037G > A in TYR, c.1211C > T, c.1441G > A, c.1706_1707insT, c.2020C > G, c.2402G > C, c.2430del, in OCA2, c.1067G > A in TYRP1 and c.451C > T, c.515G > T, c.766C > T, c.917G > A in MC1R genes were identified. Three variants in OCA2 gene were characterized: c.1706_1707insT, c.2430del, and c.2402G > C, all of which were not reported before in OCA families.

CONCLUSION

A few studies focusing on mutation screening of OCA patients have been reported before; however, this study has uniquely presents the Pakhtun ethnic population residing on the North-Western boarder. It explains that TYR, OCA2, TYRP1, and MC1R variations lead to non-syndromic OCA phenotype The overlapping phenotypes of OCA can precisely be diagnosed for its molecular pathogenicity using WES. This study recommends WES as a first-line molecular diagnostic tool, and provides a basis for developing customized genetic tests i.e. pre-marital screening to reduce the disease burden in the future generations.

Visual acuity improvement in children with albinism beyond the first decade of life

PURPOSE

To determine if visual maturation continues beyond the first decade of life in children with albinism and whether this is related to albinism type, presence of nystagmus, eye muscle surgery or refractive errors.

DESIGN

Case series based on retrospective study of children with confirmed genetic diagnosis of albinism.

METHODS

Clinical data were obtained from medical files of children examined during school years, including albinism type, visual acuity, eye muscle surgery, nystagmus, and others on different visits (Visit 1: ages 7-9; Visit 2: ages: 10-12; Visit 3: ages 13-16; Visit 4: ages >16).

RESULTS

Seventy-five children with albinism were included in the study. Patients were divided into different groups according to the albinism type including OCA1A: 17; OCA1B: 28; OCA2: 26; HPS: 3; OCA4: 1. Follow-up ranged from 3-13 years. Progressive visual acuity improvement was seen in all three main groups. T-test paired samples showed a statistically significant improvement when comparing vision from Visit 1 and Visit 3 in both OCA1A and OCA2 groups, with a mean vision improvement of 2 lines. There was no correlation between visual improvement and refractive error, eye muscle surgery or nystagmus.

CONCLUSION

An improved visual performance was seen in a large percentage of children with albinism during the second decade of life. The reason for this late improvement in vision is not clear but may be related to late foveal maturation or improvement in nystagmus with time. This information is useful for clinicians of these patients and when counseling parents.

Perinatal clinical course of Vici syndrome associated with novel EPG5 variants: unique cardiac changes and difficulty with foetal diagnosis

Vici syndrome is a genetic disorder involving autophagy dysfunction caused by biallelic pathogenic variants in ectopic P-granules 5 autophagy tethering factor (EPG5). We report the perinatal clinical course of a neonate with Vici syndrome with a unique cardiac presentation. Foetal ultrasonography (US) detected right ventricular hypertrophy, hypoplastic left ventricle and narrowing of the foramen ovale, which were alleviated after birth. Agenesis of the corpus callosum and cerebellar hypoplasia were missed antenatally. After delivery, the patient was clinically diagnosed with Vici syndrome and two novel pathogenic mutations were detected in EPG5 The T-cell receptor repertoire was selectively skewed in the Vβ2 family. Immunological prophylaxis and tube feeding were introduced. Early diagnosis helps parents accept their child's prognosis and decide on a care plan. However, US has limited potential to detect clinical phenotypes associated with Vici syndrome. Foetal MRI may detect the characteristic abnormalities and contribute to antenatal diagnosis.

Nystagmus in the B6(CG)Tyr(c-2J)/J Albino Mouse: A Functional and RNA-Seq Analysis

Purpose

Infantile nystagmus syndrome (INS) is a gaze-holding disorder characterized by conjugate, uncontrolled eye oscillations that can result in significant visual acuity loss. INS is often associated with albinism, but the mechanism is unclear. Albino mice have nystagmus; however, a pigmented mouse with a tyr mutation making it phenotypically albino, the B6(CG)-Tyr(c-2J)/J (B6 albino), had not been tested. We tested optokinetic response (OKR) in B6 albino and control mice. RNA-Seq was performed on extraocular muscles (EOM), tibialis anterior (TA) muscle, abducens (CN6), and oculomotor (CN3) neurons to uncover molecular differences that may contribute to nystagmus.

Methods

OKR was measured using an ISCAN system. RNA was isolated from four tissues to identify differentially expressed genes and validated with qPCR and immunohistochemistry. Ingenuity pathway analyses identified top biological pathways.

Results

All B6 albino mice tested had nystagmus. Differential RNA expression analysis showed 383 genes differentially expressed in EOM, 70 in CN3, 20 in CN6, and 639 in the TA. Two genes were differentially expressed in all four tissues: wdfy1 and nnt. Differences were validated by qPCR and immunostaining.

Conclusions

The tyr mutation in B6 albino mice, genotypically pigmented and phenotypically albino, is sufficient to result in spontaneous nystagmus. The two genes with decreased expression in the B6 albino tissues examined, wdfy1 and nnt, have been implicated in mitochondrial dysfunction and stem cell maintenance in other systems. Their function in extraocular muscle is unknown. These studies suggest that this mouse model of nystagmus may allow molecular identification of candidate nystagmus-related genes.

Validity of Xiphophorus fish as models for human disease

Platyfish and swordtails of the genus Xiphophorus provide a well-established model for melanoma research and have become well known for this feature. Recently, modelling approaches for other human diseases in Xiphophorus have been developed or are emerging. This Review provides a comprehensive summary of these models and discusses how findings from basic biological and molecular studies and their translation to medical research demonstrate that Xiphophorus models have face, construct and predictive validity for studying a broad array of human diseases. These models can thus improve our understanding of disease mechanisms to benefit patients.

Advances in the engineering of the outer blood-retina barrier: From in-vitro modelling to cellular therapy

The outer blood-retina barrier (oBRB), crucial for the survival and the proper functioning of the overlying retinal layers, is disrupted in numerous diseases affecting the retina, leading to the loss of the photoreceptors and ultimately of vision. To study the oBRB and/or its degeneration, many in vitro oBRB models have been developed, notably to investigate potential therapeutic strategies against retinal diseases. Indeed, to this day, most of these pathologies are untreatable, especially once the first signs of degeneration are observed. To cure those patients, a current strategy is to cultivate in vitro a mature oBRB epithelium on a custom membrane that is further implanted to replace the damaged native tissue. After a description of the oBRB and the related diseases, this review presents an overview of the oBRB models, from the simplest to the most complex. Then, we propose a discussion over the used cell types, for their relevance to study or treat the oBRB. Models designed for in vitro applications are then examined, by paying particular attention to the design evolution in the last years, the development of pathological models and the benefits of co-culture models, including both the retinal pigment epithelium and the choroid. Lastly, this review focuses on the models developed for in vivo implantation, with special emphasis on the choice of the material, its processing and its characterization, before discussing the reported pre-clinical and clinical trials.

Zebrafish Optokinetic Reflex: Minimal Reporting Guidelines and Recommendations

Optokinetic reflex (OKR) assays in zebrafish models are a valuable tool for studying a diverse range of ophthalmological and neurological conditions. Despite its increasing popularity in recent years, there are no clear reporting guidelines for the assay. Following reporting guidelines in research enhances reproducibility, reduces bias, and mitigates underreporting and poor methodologies in published works. To better understand optimal reporting standards for an OKR assay in zebrafish, we performed a systematic literature review exploring the animal, environmental, and technical factors that should be considered. Using search criteria from three online databases, a total of 109 research papers were selected for review. Multiple crucial factors were identified, including larval characteristics, sample size, fixing method, OKR set-up, distance of stimulus, detailed stimulus parameters, eye recording, and eye movement analysis. The outcome of the literature analysis highlighted the insufficient information provided in past research papers and the lack of a systematic way to present the parameters related to each of the experimental factors. To circumvent any future errors and champion robust transparent research, we have created the zebrafish optokinetic (ZOK) reflex minimal reporting guideline.

Stacked implantation of two prosthetic iris devices for patients with iris defects: A modified surgical technique

Purpose

Iris pigment deficiency in patients with oculocutaneous albinism (OCA) often causes debilitating photophobia, which is routinely managed by sequential intracapsular insertion of two aniridia rings. A common concern of this technique is the risk of segment interdigitation, which can lead to intraoperative complications.

Observations

In this report, we describe a modified technique through which both rings were stacked together and inserted simultaneously in a 62-year-old male patient with oculocutaneous albinism and a mild cataract. The patient underwent bilateral phacoemulsification followed by implantation of two Morcher 50E aniridia rings simultaneously, prior to IOL implantation behind the implants within the capsular bag. Post-operatively, the patient's photophobia improved dramatically, and there were no post-operative complications.

Conclusions and Importance

Simultaneous insertion of two stacked aniridia rings prior to IOL implantation was a safe and successful alternative surgical method for the management of photophobia in patients with oculocutaneous albinism and cataracts.

Malignancies in Prader-Willi Syndrome: Results From a Large International Cohort and Literature Review

CONTEXT

Prader-Willi syndrome (PWS) is a complex disorder combining hypothalamic dysfunction, neurodevelopmental delay, hypotonia, and hyperphagia with risk of obesity and its complications. PWS is caused by the loss of expression of the PWS critical region, a cluster of paternally expressed genes on chromosome 15q11.2-q13. As life expectancy of patients with PWS increases, age-related diseases like malignancies might pose a new threat to health.

OBJECTIVE

To investigate the prevalence and risk factors of malignancies in patients with PWS and to provide clinical recommendations for cancer screening.

METHODS

We included 706 patients with PWS (160 children, 546 adults). We retrospectively collected data from medical records on past or current malignancies, the type of malignancy, and risk factors for malignancy. Additionally, we searched the literature for information about the relationship between genes on chromosome 15q11.2-q13 and malignancies.

RESULTS

Seven adults (age range, 18-55 years) had been diagnosed with a malignancy (acute lymphoblastic leukemia, intracranial hemangiopericytoma, melanoma, stomach adenocarcinoma, biliary cancer, parotid adenocarcinoma, and colon cancer). All patients with a malignancy had a paternal 15q11-13 deletion. The literature review showed that several genes on chromosome 15q11.2-q13 are related to malignancies.

CONCLUSION

Malignancies are rare in patients with PWS. Therefore, screening for malignancies is only indicated when clinically relevant symptoms are present, such as unexplained weight loss, loss of appetite, symptoms suggestive of paraneoplastic syndrome, or localizing symptoms. Given the increased cancer risk associated with obesity, which is common in PWS, participation in national screening programs should be encouraged.

Human equivalent doses of L-DOPA rescues retinal morphology and visual function in a murine model of albinism

L-DOPA is deficient in the developing albino eye, resulting in abnormalities of retinal development and visual impairment. Ongoing retinal development after birth has also been demonstrated in the developing albino eye offering a potential therapeutic window in humans. To study whether human equivalent doses of L-DOPA/Carbidopa administered during the crucial postnatal period of neuroplasticity can rescue visual function, OCA C57BL/6 J-c2J OCA1 mice were treated with a 28-day course of oral L-DOPA/Carbidopa at 3 different doses from 15 to 43 days postnatal age (PNA) and for 3 different lengths of treatment, to identify optimum dosage and treatment length. Visual electrophysiology, acuity, and retinal morphology were measured at 4, 5, 6, 12 and 16 weeks PNA and compared to untreated C57BL/6 J (WT) and OCA1 mice. Quantification of PEDF, βIII-tubulin and syntaxin-3 expression was also performed. Our data showed impaired retinal morphology, decreased retinal function and lower visual acuity in untreated OCA1 mice compared to WT mice. These changes were diminished or eliminated when treated with higher doses of L-DOPA/Carbidopa. Our results demonstrate that oral L-DOPA/Carbidopa supplementation at human equivalent doses during the postnatal critical period of retinal neuroplasticity can rescue visual retinal morphology and retinal function, via PEDF upregulation and modulation of retinal synaptogenesis, providing a further step towards developing an effective treatment for albinism patients.

Chromosome-level reference genome for North American bison (Bison bison) and variant database aids in identifying albino mutation

We developed a highly contiguous chromosome-level reference genome for North American bison to provide a platform to evaluate the conservation, ecological, evolutionary, and population genomics of this species. Generated from a F1 hybrid between a North American bison dam and a domestic cattle bull, completeness and contiguity exceed that of other published bison genome assemblies. To demonstrate the utility for genome-wide variant frequency estimation, we compiled a genomic variant database consisting of 3 true albino bison and 44 wild-type pelage color bison. Through the examination of genomic variants fixed in the albino cohort and absent in the controls, we identified a nonsynonymous single nucleotide polymorphism (SNP) mutation on chromosome 29 in exon 3 of the tyrosinase gene (c.1114C>T). A TaqMan SNP Genotyping Assay was developed to genotype this SNP in a total of 283 animals across 29 herds. This assay confirmed the absence of homozygous variants in all animals except 7 true albino bison included in this study. In addition, the only heterozygous animals identified were 2 wild-type pelage color dams of albino offspring. Therefore, we propose that this new high-quality bison genome assembly and incipient variant database provides a highly robust and informative resource for genomics investigations for this iconic North American species.

Ophthalmologic Phenotype-Genotype Correlations in Patients With Oculocutaneous Albinism Followed in a Reference Center

Purpose

Albinism is a group of genetic disorders that includes several conditions related to a defect in melanin production. There is a broad phenotypic and genotypic variability between the different forms. The aim of this study was to assess the ophthalmologic characteristics according to patients' genotypes in a cohort followed in the Reference Center for oculocutaneous albinism (OCA) of Bordeaux University Hospital, France.

Methods

A retrospective observational study was conducted in a cohort of patients with OCA seen in consultation in the ophthalmology department between 2017 and 2021 in whom a genetic analysis was performed.

Results

In total, 127 patients with OCA were included in this study and matched with the results of the genetic analysis. In the population aged over 6 years, there was no statistical difference in binocular visual acuity between the OCA1, OCA2, and OCA4 forms (P = 0.27). There was difference in ametropia between the three forms (P = 0.003). A two-by-two comparison using the Bonferroni correction showed a significant difference in ametropia between the OCA2 and OCA4 forms (P = 0.007) and between the OCA1 and OCA2 forms (P = 0.0075). Regardless of the form, most patients (75.4%) had grade 4 foveal hypoplasia. There was no association between the grade of foveal hypoplasia and the gene involved (P = 0.87).

Conclusions

We described a genotype-phenotype correlation for the three most represented forms of albinism in our cohort. This study allowed assessing the degree of visual deficiency in young children with OCA.

Photosensitivity and filter efficacy in albinism✰

PURPOSE

To describe the prevalence and severity of photosensitivity in patients with albinism, and to compare with ocular features and how this correlated with use and choice of optical filters.

METHODS

Cross-sectional study on 81 participants with ocular or oculocutaneous albinism. An ophthalmic evaluation including visual acuity, contrast sensitivity and evaluation of iris translucency and fundus hypopigmentation was performed. Participants were offered optical rehabilitation with testing of a wide panel of filters. The associations between ocular characteristics, subjective photosensitivity complaints, and filter choice were evaluated.

RESULTS

Photosensitivity was rated as "some" to "worst imaginable" in 77.8% of participants. Severity of photosensitivity correlated significantly with fundus hypopigmentation (p = 0.04) but not with iris translucency (p = 0.14) and it was worse in those with poor visual acuity but there was no association between photosensitivity and contrast vision. Seventy-four new pairs of spectacles were prescribed in the study. All outdoor spectacles contained a filter, whereas 26.5% of new indoor spectacles did not. Relatively neutral filter colors (gray, brown or a combination of gray and brown with other colors) and low transmission were preferred.

DISCUSSION

Photosensitivity is common in albinism, but research targeting treatment is limited. Color and neutral filters with a low light transmission were preferred, with participants having a large number of spectacles, presumably to meet their needs in different situations.