Bi-allelic Mutations in LSS, Encoding Lanosterol Synthase, Cause Autosomal-Recessive Hypotrichosis Simplex

ATR promotes mTORC1 activity via de novo cholesterol synthesis

DNA damage and cellular metabolism exhibit a complex interplay characterized by bidirectional feedback. Key mediators of these pathways include ATR and mTORC1, respectively. Previous studies established ATR as a regulatory upstream factor of mTORC1 during replication stress; however, the precise mechanisms remain poorly defined. Additionally, the activity of this signaling axis in unperturbed cells has not been extensively investigated. We demonstrate that ATR promotes mTORC1 activity across various human cancer cells and both human and mouse normal cells under basal conditions. This effect is enhanced in human cancer cells (SKMEL28, RPMI-7951, HeLa) following knockdown of p16, a cell cycle inhibitor that we have previously found increases mTORC1 activity and here found increases ATR activity. Mechanistically, ATR promotes de novo cholesterol synthesis and mTORC1 activation through the phosphorylation and upregulation of lanosterol synthase (LSS), independently of both CHK1 and the TSC complex. Interestingly, this pathway is distinct from the regulation of mTORC1 by ATM and may be specific to cancer cells. Finally, ATR-mediated increased cholesterol correlates with enhanced localization of mTOR to lysosomes. Collectively, our findings demonstrate a novel connection linking ATR and mTORC1 signaling through the modulation of cholesterol metabolism.

A novel LSS variant leading to hypotrichosis with pseudoainhum

Congenital alopecia/hypotrichosis constitutes a spectrum of rare inherited hair disorders characterized by partial to complete alopecia and possible structural hair shaft defects. The lanosterol synthase (LSS) gene, implicated in cholesterol biosynthesis, has emerged as a novel genetic determinant of congenital hypotrichosis. This article describes a 43-year-old female with congenital lanugo-like scalp hair and absence of eyebrows who later developed painful fibrotic constrictive bands on her fingers, culminating in pseudoainhum, but without manifestations of typical palmoplantar keratoderma (PPK). Whole-exome sequencing detected a novel homozygous variant (c.508G>A; p. Asp170Asn) in the LSS gene. This case delineates an atypical LSS variant presentation associated with pseudoainhum phenotype, manifesting without classic PPK features, a previously unreported phenotypic combination. Our findings expand the phenotypic spectrum of LSS-related disorders and underscore the potential role of lipid signaling in hair follicle biology and the pseudoainhum phenomenon.

Paediatric Hypotrichosis: A Clinical and Algorithmic Approach to Diagnosis

Paediatric hypotrichosis is the clinical feature of paucity of hair arising congenitally or in early life with the presentation being that of the child whose hair is growing insufficiently. It is a hallmark finding of a diverse group of genodermatoses and sporadic disorders, presenting as either an isolated symptom or in association with syndromic features. Hypotrichoses are rare, with numerous possible differentials requiring a thorough clinical assessment, additional investigations for hair shaft abnormalities and occasionally genetic counselling to reach a diagnosis. We propose a clinical algorithm for the investigation and diagnosis of paediatric hypotrichosis, designed to aid the clinician by utilising key clinical findings in conjunction with the forced hair pull test and trichoscopy to differentiate groups of hair shaft and hair loss disorders. We also discuss in further detail the pathogenesis, phenotypical features and microscopy findings of various types of hypotrichosis.

Congenital hypotrichosis caused by compound heterozygous variants in the LSS gene in a Chinese patient with strabismus: case report

Background

Lanosterol synthase (LSS) is essential for cholesterol biosynthesis and impacts embryonic development and growth. LSS gene variants have been associated with various conditions such as congenital hypotrichosis and cataracts, but the genotype-phenotype relationship remains not well understood.

Case presentation

Herein, we report an 8-year-old boy presenting with congenital hypotrichosis and intermittent exotropia, but without any ocular movement abnormalities or cataracts. His hair exhibited sparse distribution with a yellow color, reduced strength, and minimal growth. Scanning electron microscopy revealed abnormal keratinization of the hair shafts, characterized by irregular, jagged scales and raised edges. Whole-exome sequencing identified compound heterozygous missense variants in the LSS gene: c.1303C>T (p.Arg435Cys) and c.386G>A (p.Arg129Gln). Three-dimensional protein modeling revealed that these variants affect highly conserved amino acid residues and are predicted by computational tools to destabilize the protein. Based on ACMG guidelines, both variants were classified as likely pathogenic, consistent with the patient's phenotype.

Conclusion

We present a rare case of LSS-related hypotrichosis with strabismus and a novel c.386G>A variant has not been reported, which broadens the understanding of LSS gene variants and their phenotypic spectrum, enhancing insights into the genotype-phenotype relationship in LSS-related conditions.

Molecular Basis of Hereditary Hair Diseases

The hair follicle is an appendage of the skin that undergoes hair cycles throughout life. Recently, numerous genes expressed in the hair follicles have been identified, and variants in some of these genes are now known to underlie hereditary hair diseases in humans. Hereditary hair diseases are classified into non-syndromic and syndromic forms. In the Japanese population, the non-syndromic form of autosomal recessive woolly hair, which is caused by founder pathogenic variants in the lipase H (LIPH) gene, is the most prevalent hereditary hair disease. In addition, other types of hereditary hair diseases are known in Japan, such as Marie-Unna hereditary hypotrichosis, hypohidrotic ectodermal dysplasia, and tricho-rhino-phalangeal syndrome. To ensure correct diagnoses and appropriate patient care, dermatologists must understand the characteristics of each hair disorder. Elucidation of the molecular basis of hereditary hair diseases can directly tell us which genes are crucial for morphogenesis and development of hair follicles in humans. Therefore, continuation of "wet laboratory" research for these diseases remains important. To date, several syndromic forms of hereditary hair diseases have been approved as designated intractable diseases in Japan. As part of our efforts in the Project for Research on Intractable Diseases through the Ministry of Health, Labour, and Welfare of Japan, we anticipate that more hereditary hair diseases be recognized as designated intractable diseases in the future, which will be to the benefit of the affected individuals.

Biallelic pathogenic variants in the LSS gene cause congenital alopecia-cataract syndrome

Biallelic variants in the LSS gene have been reported in individuals affected by alopecia-intellectual disability syndrome 4, cataract 44, hypotrichosis 14, and palmoplantar keratoderma-congenital alopecia syndrome type 2. The present report described a Chinese girl with congenital alopecia universalis, cataract, esotropia, and nystagmus caused by compound heterozygous variants of c.1025T>G (p.Ile342Ser) and previously unreported c.1011G>A (p.Pro337=) in the LSS gene. Minigene assay confirmed the synonymous variant Pro337= at the edge of exon 9 could produce a novel splice site, leading to a 46-bp insertion of the 5' sequence of the intron 9, likely resulting in a frameshift effect. We consider that the clinical manifestations of this case represent a new type of LSS-related disease, namely congenital alopecia-cataract syndrome (CACS). Our data expand the phenotypic and genetic spectrum of LSS-related diseases.

Embryotoxicity of statins and other prescribed drugs with reported off-target effects on cholesterol biosynthesis

Cholesterol plays pivotal cellular functions ranging from maintaining membrane fluidity to regulating cell-cell signaling. High cholesterol causes cardiovascular diseases, low cholesterol is linked to neuropsychiatric disorders, and inborn errors of cholesterol synthesis cause multisystem malformation syndromes. Statins lower cholesterol levels by inhibiting the first, rate-limiting reaction of the cholesterol biosynthesis pathway catalyzed by hydroxymethyl-glutaryl-Coenzyme A reductase (HMGCR). However, they have also been shown to interfere with cellular pathways that are unrelated to cholesterol synthesis. One of the last enzymes of cholesterol biosynthesis, 7-dehydrocholesterol reductase (DHCR7), is often mutated in the Smith-Lemli-Opitz syndrome (SLOS), a multisystem malformation syndrome. Strikingly, recent studies have shown that some prescribed psychotropic pharmaceuticals inhibit its activity. In this study, we used Xenopus laevis as a model organism to test the effects of 8 FDA-approved statins and selected prescribed psychotropic drugs on the developing vertebrate embryo. Drugs were tested at concentrations ranging from 0.1 µM to 50 µM. Embryos were exposed to the drugs from the blastula stage through the swimming tadpole stage with daily medium change. Our data show that statins are heterogenous with respect to their ability to cause embryonic lethality, with simvastatin, pitavastatin, lovastatin, cerivastatin, and fluvastatin being the most toxic ones. Observed phenotypes included delayed development, shortened body axis and pericardiac edema. On the other hand, psychotropic drugs were less embryonic lethal than statins but caused similar phenotypes as well as microcephaly and holoprosencephaly. Our findings suggest that the proximal and distal inhibition of cholesterol biosynthesis have different but overlapping effects on embryonic development.

Altered chromatin topologies caused by balanced chromosomal translocation lead to central iris hypoplasia

Despite the advent of genomic sequencing, molecular diagnosis remains unsolved in approximately half of patients with Mendelian disorders, largely due to unclarified functions of noncoding regions and the difficulty in identifying complex structural variations. In this study, we map a unique form of central iris hypoplasia in a large family to 6q15-q23.3 and 18p11.31-q12.1 using a genome-wide linkage scan. Long-read sequencing reveals a balanced translocation t(6;18)(q22.31;p11.22) with intergenic breakpoints. By performing Hi-C on induced pluripotent stem cells from a patient, we identify two chromatin topologically associating domains spanning across the breakpoints. These alterations lead the ectopic chromatin interactions between APCDD1 on chromosome 18 and enhancers on chromosome 6, resulting in upregulation of APCDD1. Notably, APCDD1 is specifically localized in the iris of human eyes. Our findings demonstrate that noncoding structural variations can lead to Mendelian diseases by disrupting the 3D genome structure and resulting in altered gene expression.

Clinical and genetic analyses of APMR4 syndrome caused by novel biallelic LSS variants

Alopecia intellectual disability syndromes 4 (APMR4) caused by Lanosterol synthase (LSS) gene variants is a very rare autosomal recessive neuroectodermal syndrome. It is characterized by congenital alopecia and variable degrees of intellectual disability (ID), frequently associated with developmental delay (DD) and epilepsy. Currently, only three studies regarding LSS-related APMR4 have been reported, the pathogenesis of APMR4 is poorly understood. We studied one patient with LSS-related APMR4 who presented with severe intellectual disability, alopecia, early-onset epilepsy and developmental delay. She is absence of hair on the eyebrows, eyelashes, and scalp. Two novel LSS variants (c.401 T > G and c.369C > G) were detected with whole-exome sequencing (WES). Analysis via WB experiment indicated that c.369 > G reduced the protein expression level of LSS. Analysis of protein stability prediction showed a destabilizing for LSS caused by the variant c.401 T > G. This study is the first study in Asia to date. These findings expanded the variantal spectrum of LSS-related APMR4 and revealed the potential pathogenic mechanism of LSS gene variants.

Chemical Inhibition of Sterol Biosynthesis

Cholesterol is an essential molecule of life, and its synthesis can be inhibited by both genetic and nongenetic mechanisms. Hundreds of chemicals that we are exposed to in our daily lives can alter sterol biosynthesis. These also encompass various classes of FDA-approved medications, including (but not limited to) commonly used antipsychotic, antidepressant, antifungal, and cardiovascular medications. These medications can interfere with various enzymes of the post-lanosterol biosynthetic pathway, giving rise to complex biochemical changes throughout the body. The consequences of these short- and long-term homeostatic disruptions are mostly unknown. We performed a comprehensive review of the literature and built a catalogue of chemical agents capable of inhibiting post-lanosterol biosynthesis. This process identified significant gaps in existing knowledge, which fall into two main areas: mechanisms by which sterol biosynthesis is altered and consequences that arise from the inhibitions of the different steps in the sterol biosynthesis pathway. The outcome of our review also reinforced that sterol inhibition is an often-overlooked mechanism that can result in adverse consequences and that there is a need to develop new safety guidelines for the use of (novel and already approved) medications with sterol biosynthesis inhibiting side effects, especially during pregnancy.

A case of congenital cataracts with hypotrichosis caused by compound heterozygous variants in the LSS gene

BACKGROUND

Patients with biallelic variants in the lanosterol synthase (LSS) gene has been reported to exhibit phenotypes as follows: non-syndromic form of hypotrichosis, congenital cataracts, and alopecia with intellectual disability or growth retardation. However, genotype-phenotype correlations in the LSS gene are still not completely clear.

METHODS

In this study, we reported a Chinese girl who had congenital cataracts with hypotrichosis. The trio exome sequencing was performed to elucidate the genetic cause of the patient.

RESULTS

We identified compound heterozygous variants (c.296G>A, p.G99D and c.1025T>G, p.I342S) in the LSS gene. Both variants altered the amino acid coding at highly conserved amino acid residues and were predicted to be deleterious using prediction software.

CONCLUSION

Our report expands the spectrum of variants in the LSS gene and will be helpful for genotype-phenotype correlations study.

The history of Coast Salish "woolly dogs" revealed by ancient genomics and Indigenous Knowledge

Ancestral Coast Salish societies in the Pacific Northwest kept long-haired "woolly dogs" that were bred and cared for over millennia. However, the dog wool-weaving tradition declined during the 19th century, and the population was lost. In this study, we analyzed genomic and isotopic data from a preserved woolly dog pelt from "Mutton," collected in 1859. Mutton is the only known example of an Indigenous North American dog with dominant precolonial ancestry postdating the onset of settler colonialism. We identified candidate genetic variants potentially linked with their distinct woolly phenotype. We integrated these data with interviews from Coast Salish Elders, Knowledge Keepers, and weavers about shared traditional knowledge and memories surrounding woolly dogs, their importance within Coast Salish societies, and how colonial policies led directly to their disappearance.

Prenatal diagnosis of lanosterol synthase deficiency: Fetal ultrasound findings as a window on family genetics

Cholesterol is essential in the brain from the earliest stages of embryonic development. Disruption of cholesterol synthesis pathways that leads to cholesterol deficiency underlies a few syndromes, including desmosterolosis and Smith-Lemli-Opitz syndrome. In both syndromes, brain anomalies can occur. The LSS gene encodes lanosterol synthase (LSS), an important enzyme in the cholesterol biosynthesis pathway. Biallelic pathogenic variants in this gene cause alopecia-intellectual disability type 4 syndrome (APMR4, MIM 618840), a rare autosomal recessive disorder. Here, we describe two new LSS variants (c.1016C > T; p. Ser339Leu and c.1522G > C; p. Gly508Arg) found in a compound heterozygous fetus diagnosed prenatally with brain abnormalities by ultrasound scanning. Two of his siblings from the same parents also harbored these variants. Both siblings had alopecia, mild intellectual disability, autism spectrum disorder, and cataracts. To the best of our knowledge, this case represents the first prenatal diagnosis of APMR4 first suspected by ultrasound. In addition, the phenotypic features of the siblings are extensive compared with those described in previous reports and include abnormal corpus callosum, cataracts, alopecia, and developmental delay.

HUB genes transcriptionally regulate lipid metabolism in alveolar type II cells under LPS stimulation

Objective

Alveolar type II (ATII) cells produce pulmonary surfactant (PS) essential for maintaining lung function. The aberration or depletion of PS can cause alveolar collapse, a hallmark of acute respiratory distress syndrome (ARDS). However, the intricacies underlying these changes remain unclear. This study aimed to elucidate the mechanisms underlying PS perturbations in ATII cells using transcriptional RNA-seq, offering insights into the pathogenesis of ARDS.

Methods

ATII cells were identified using immunofluorescence targeting surface-active protein C. We used 24-h lipopolysaccharide (LPS)-induced ATII cells as an ARDS cell model. The efficacy of the injury model was gauged by detecting the presence of tumour necrosis factor-α and interleukin-6. RNA-seq analysis was performed to investigate the dynamics of PS deviation in unaltered and LPS-exposed ATII cells.

Results

Whole-transcriptome sequencing revealed that LPS-stimulated ATII cells showed significantly increased transcription of genes, including Lss, Nsdhl, Hmgcs1, Mvd, Cyp51, Idi1, Acss2, Insig1, and Hsd17b7, which play key roles in regulating cholesterol biosynthesis. We further verified gene levels using real-time quantitative PCR, and the results showed that the mRNA expression of these genes increased, which was consistent with the RNA-seq results.

Conclusion

Our study revealed pivotal transcriptional shifts in ATII cells after LPS exposure, particularly in nine key lipid and cholesterol metabolism genes. This altered expression might disrupt the lipid balance, ultimately affecting PS function. This finding deepens our understanding of the aetiology of ARDS and may lead to new therapeutic directions.

Non-syndromic hypotrichosis: A report of two novel variants in the LSS gene

To date, more than 15 genes have been linked to syndromic and non-syndromic hypotrichosis, among which the LSS gene encoding lanosterol synthase was recently linked to autosomal recessive isolated hypotrichosis. Here we report the case of a 6-year-old girl born to non-consanguineous Iraqi parents and presenting with sparse lanugo hair since birth on the scalp, eyelashes, and eyebrows. Whole exome sequencing followed by Sanger sequencing allowed the detection of two novel compound heterozygous variants in LSS (p.Ile323Thr and p.Gly600Val). Reporting and investigating further cases with LSS variants might help establishing a better genotype-phenotype correlation.

A case of LSS-associated congenital nuclear cataract with hypotrichosis and literature review

Congenital cataract is the most common cause of lifelong visual loss in children worldwide, which has significant genotypic and phenotypic heterogeneity. The LSS gene encodes lanosterol synthase (LSS), which acts on the cholesterol biosynthesis pathway by converting (S)-2,3-oxidosqualene to lanosterol. The biallelic pathogenic variants in the LSS gene were found in congenital cataract, Alopecia-intellectual disability syndrome, hypotrichosis simplex, and mutilating palmoplantar keratoderma. In this study, we reported the first congenital nuclear cataract combined with hypotrichosis in a 12-year-old boy with biallelic LSS variants (c.1025T>G; p.I342S and c.1531_1532insT; p.L511Ffs*17) by exome sequencing. Reviewing all reported patients with LSS variants indicated that p.W629 might be a hotspot for hypospadias and p.I342S was associated with congenital cataract. Patients with one or two truncation variants tend to have multisystem symptoms compared with those with two missense variants. These findings deepen the understanding of LSS variants and contribute to the genetic counseling of affected families.

Novel LSS variants in alopecia and intellectual disability syndrome: New case report and clinical spectrum of LSS-related rare disease traits

Pathogenic biallelic variants in LSS are associated with three Mendelian rare disease traits including congenital cataract type 44, autosomal recessive hypotrichosis type 14, and alopecia-intellectual disability syndrome type 4 (APMR4). We performed trio research exome sequencing on a family with a four-year-old male with global developmental delay, epilepsy and striking alopecia, and identified novel compound heterozygous LSS splice site (c.14+2T>C) and missense (c.1357 G>A; p.V453L) variant alleles. Rare features associated with APMR4 such as cryptorchidism, micropenis, mild cortical brain atrophy and thin corpus callosum were detected. Previously unreported APMR4 findings including cerebellar involvement in the form of unsteady ataxic gait, small vermis with prominent folia, were noted. A review of all reported variants to date in 29 families with LSS-related phenotypes showed an emerging genotype-phenotype correlation. Our report potentially expands LSS-related phenotypic spectrum and highlights the importance of performing brain imaging in LSS-related conditions.

A novel compound heterozygous variant in the LLS gene is associated with nonsyndromic hypotrichosis

This report described a patient presenting with hypotrichosis simplex associated with compound heterozygosity for two novel LSS mutations. The clinical manifestations associated with mutations in the LSS gene, which is involved in sterol synthesis, are highly variable, ranging from simple hypotrichosis to alopecia with intellectual disability or cataracts. The identification of more patients and further functional studies are needed to improve the understanding of the pathophysiological mechanisms of LSS-related conditions.

Development of Woolly Hair and Hairlessness in a CRISPR-Engineered Mutant Mouse Model with KRT71 Mutations

Hypotrichosis simplex (HS) and woolly hair (WH) are rare and monogenic disorders of hair loss. HS, characterized by a diffuse loss of hair, usually begins in early childhood and progresses into adulthood. WH displays strong coiled hair involving a localized area of the scalp or covering the entire side. Mutations in the keratin K71(KRT71) gene have been reported to underlie HS and WH. Here, we report the generation of a mouse model of HS and WH by the co-injection of Cas9 mRNA and sgRNA, targeting exon6 into mouse zygotes. The Krt71-knockout (KO) mice displayed the typical phenotypes, including Krt71 protein expression deletion and curly hair in their full body. Moreover, we found that mice in 3-5 weeks showed a new phenomenon of the complete shedding of hair, which was similar to nude mice. However, we discovered that the mice exhibited no immune deficiency, which was a typical feature of nude mice. To our knowledge, this novel mouse model generated by the CRISPR/Cas9 system mimicked woolly hair and could be valuable for hair disorder studies.

Comparative Analyses Reveal the Genetic Mechanism of Ambergris Production in the Sperm Whale Based on the Chromosome-Level Genome

Sperm whales are a marine mammal famous for the aromatic substance, the ambergris, produced from its colon. Little is known about the biological processes of ambergris production, and this study aims to investigate the genetic mechanism of ambergris production in the sperm whale based on its chromosome-level genome. Comparative genomics analyses found 1207 expanded gene families and 321 positive selected genes (PSGs) in the sperm whale, and functional enrichment analyses suggested revelatory pathways and terms related to the metabolism of steroids, terpenoids, and aldosterone, as well as microbiota interaction and immune network in the intestine. Furthermore, two sperm-whale-specific missense mutations (Tyr393His and Leu567Val) were detected in the PSG LIPE, which has been reported to play vital roles in lipid and cholesterol metabolism. In total, 46 CYP genes and 22 HSD genes were annotated, and then mapped to sperm whale chromosomes. Furthermore, phylogenetic analysis of CYP genes in six mammals found that CYP2E1, CYP51A and CYP8 subfamilies exhibited relative expansion in the sperm whale. Our results could help understand the genetic mechanism of ambergris production, and further reveal the convergent evolution pattern among animals that produce similar odorants.

A novel homozygous mutation in LSS gene possibly causes hypotrichosis simplex in two siblings of a Tibetan family from the western Sichuan province of China

Aim: Hypotrichosis simplex (MIM 146520) is a rare form of monogenic hereditary alopecia. Several genes have been identified as being associated with the disease, including LPAR6, LIPH, and DSG4. LSS encoding lanosterol synthase (LSS) has been shown to cause hypotrichosis simplex, but the related mechanisms have not been elucidated to date. This study aims to find mutations in LSS from a Chinese family, among which a 21-year-old male patient and his 9-year-old sister were affected by hypotrichosis simplex. Methods: Dermoscopy and histological analysis were used to examine patients' scalps, while exome sequencing was used to find the mutations in LSS. Results: The hair loss was only detected on the scalp of the proband and his sister, while other ectodermal structures were normal with no systemic abnormalities. Further, the exome sequencing identified a new homozygous mutation NM_002340.6 (LSS_v001):c.812T>C (p.(Ile271Thr)) in the LSS gene of the proband, which was also found in his sister. In addition, a heterozygous mutation of LSS was found in their asymptomatic parents. Finally, the possible protein structure of the mutational LSS was predicted. Conclusion: The hypotrichosis simplex reported here could be an autosomal recessive disease in this family. The mutation on LSS might reduce the enzyme activity of LSS, thus leading to the disease.

Progressive Hair Loss With Short Hair in a Child

A school-aged girl presented to the dermatology clinic with a 6-year history of hair loss and short hair, and light microscopy of scalp hair shafts revealed no structural abnormalities, such as cuticular damage, twisting, bending, or miniaturization. What is your diagnosis?

Alopecia and hyperpigmentation in a neonatal patient with lanosterol synthase gene deficiency and Spectrin alpha, non-erythrocytic 1 mutation

Lanosterol synthase is required for cholesterol synthesis, and deficiencies have been associated with hypotrichosis as well as neuroectodermal syndromes including intellectual delay and epilepsy. Here, we report a case of lanosterol synthase deficiency in a 4-day-old patient who presented with alopecia and a previously unreported dermatologic manifestation of congenital localized hyperpigmentation.

Expanding the Phenotypic Spectrum of APMR4 Syndrome Caused by a Novel Variant in LSS Gene and Review of Literature

Alopecia intellectual disability syndromes 4 (APMR4) is a very rare autosomal recessive condition caused by a mutation in the LSS gene present on chromosome 21. This syndrome has a clinical heterogeneity mainly exhibited with variable degrees of intellectual disability (ID) and congenital alopecia, as well. Eight families with 13 cases have been previously reported. Herein, we provide a report on an Egyptian family with two affected siblings and one affected fetus who was diagnosed prenatally. Whole-exome sequencing (WES) revealed a novel pathogenic missense variant (c.1609G > T; p.Val537Leu) in the lanosterol synthase gene (LSS) related to the examined patients. The detected variant was confirmed by Sanger sequencing. Segregation analyses confirmed that the parents were heterozygous. Our patient was presented with typical clinical manifestations of the disease in addition to new phenotypic features which included some dysmorphic facies as frontal bossing and bilateral large ears, as well as bilateral hyperextensibility of the fingers and wrist joints, short stature, umbilical hernia, and teeth mineralization defect. This study is the first study in Egypt and the 9th molecularly proven family to date. The aim is to expand the clinical and mutational spectrum of the syndrome. Moreover, the report gives a hint on the importance of prenatal testing and the proper genetic counseling to help the parents to take their own decision based on their beliefs.

Defect of LSS Disrupts Lens Development in Cataractogenesis

Congenital cataract is one of the leading causes of blindness in children worldwide. About one-third of congenital cataracts are caused by genetic defects. LSS, which encodes lanosterol synthase, is a causal gene for congenital cataracts. LSS is critical in preventing abnormal protein aggregation of various cataract-causing mutant crystallins; however, its roles in lens development remain largely unknown. In our study, we generated a mouse model harboring Lss G589S mutation, which is homologous to cataract-causing G588S mutation in human LSS. Lss^G589S/G589S mice exhibited neonatal lethality at postal day 0 (P0), whereas these mice showed severe opacity in eye lens. Also, we found that cataract was formed at E17.5 after we examined the opacity of embryonic lens from E13.5 to E18.5. Moreover, disrupted lens differentiation occurred at E14.5 prior to formation of the opacity of eye lens, shown as delayed differentiation of lens secondary fiber and disordered lens fiber organization. In addition, RNA-seq analysis indicated that cholesterol synthesis signaling pathways were significantly downregulated. Overall, our findings provide clear evidence that a mouse model harboring a homozygous Lss G589S mutation can recapitulate human congenital cataract. Our study points out that LSS functions as a critical determinant of lens development, which will contribute to better understanding LSS defects in cataractogenesis and developing therapies for cataracts.

Update of recent findings in genetic hair disorders

Genetic hair disorders, although unusual, are not very rare, and dermatologists often have opportunities to see patients. Significant advances in molecular genetics have led to identifying many causative genes for genetic hair disorders, including the recently identified causative genes, such as LSS and C3ORF52. Many patients have been detected with autosomal recessive woolly hair/hypotrichosis in the Japanese population caused by founder mutations in the LIPH gene. Additionally, many patients with genetic hair disorders caused by other genes have been reported in East Asia including Japan. Understanding genetic hair disorders is essential for dermatologists, and the findings obtained from analyzing these diseases will contribute to revealing the mechanisms of hair follicle morphogenesis and development in humans.

A KRT71 Loss-of-Function Variant Results in Inner Root Sheath Dysplasia and Recessive Congenital Hypotrichosis of Hereford Cattle

Genodermatoses, such as heritable skin disorders, mostly represent Mendelian conditions. Congenital hypotrichosis (HY) characterize a condition of being born with less hair than normal. The purpose of this study was to characterize the clinicopathological phenotype of a breed-specific non-syndromic form of HY in Hereford cattle and to identify the causative genetic variant for this recessive disorder. Affected calves showed a very short, fine, wooly, kinky and curly coat over all parts of the body, with a major expression in the ears, the inner part of the limbs, and in the thoracic-abdominal region. Histopathology showed a severely altered morphology of the inner root sheath (IRS) of the hair follicle with abnormal Huxley and Henle’s layers and severely dysplastic hair shafts. A genome-wide association study revealed an association signal on chromosome 5. Homozygosity mapping in a subset of cases refined the HY locus to a 690 kb critical interval encompassing a cluster of type II keratin encoding genes. Protein-coding exons of six positional candidate genes with known hair or hair follicle function were re-sequenced. This revealed a protein-changing variant in the KRT71 gene that encodes a type II keratin specifically expressed in the IRS of the hair follicle (c.281delTGTGCCCA; p.Met94AsnfsX14). Besides obvious phenocopies, a perfect concordance between the presence of this most likely pathogenic loss-of-function variant located in the head domain of KRT71 and the HY phenotype was found. This recessive KRT71-related form of hypotrichosis provides a novel large animal model for similar human conditions. The results have been incorporated in the Online Mendelian Inheritance in Animals (OMIA) database (OMIA 002114-9913).

A Nonsense Variant in Hephaestin Like 1 (HEPHL1) Is Responsible for Congenital Hypotrichosis in Belted Galloway Cattle

Genodermatosis such as hair disorders mostly follow a monogenic mode of inheritance. Congenital hypotrichosis (HY) belong to this group of disorders and is characterized by abnormally reduced hair since birth. The purpose of this study was to characterize the clinical phenotype of a breed-specific non-syndromic form of HY in Belted Galloway cattle and to identify the causative genetic variant for this recessive disorder. An affected calf born in Switzerland presented with multiple small to large areas of alopecia on the limbs and on the dorsal part of the head, neck, and back. A genome-wide association study using Swiss and US Belted Galloway cattle encompassing 12 cases and 61 controls revealed an association signal on chromosome 29. Homozygosity mapping in a subset of cases refined the HY locus to a 1.5 Mb critical interval and subsequent Sanger sequencing of protein-coding exons of positional candidate genes revealed a stop gain variant in the HEPHL1 gene that encodes a multi-copper ferroxidase protein so-called hephaestin like 1 (c.1684A>T; p.Lys562*). A perfect concordance between the homozygous presence of this most likely pathogenic loss-of-function variant and the HY phenotype was found. Genotyping of more than 700 purebred Swiss and US Belted Galloway cattle showed the global spread of the mutation. This study provides a molecular test that will permit the avoidance of risk matings by systematic genotyping of relevant breeding animals. This rare recessive HEPHL1-related form of hypotrichosis provides a novel large animal model for similar human conditions. The results have been incorporated in the Online Mendelian Inheritance in Animals (OMIA) database (OMIA 002230-9913).

Alopecia-mental retardation syndrome: Molecular genetics of a rare neuro-dermal disorder

Alopecia-mental retardation syndrome (APMR) is a rare autosomal recessive neuro-dermal disorder. It is characterized by heterogeneous phenotypic features, that is, absence of hair on the scalp, eyelashes, and eyebrows and mild to severe intellectual disability. So far, approximately 14 families (i.e., Iranian, Pakistani, and Swiss) with APMR have been reported in the scientific literature. Its precise prevalence is still unknown, but according to a predictive estimate, it prevails with the ratio of 1 in 1,000,000 persons worldwide. Until now, only four loci (two characterized and two uncharacterized) have been reported to be involved in APMR. The pathogenic variants in alpha-2-HS-glycoprotein [AHSG; APMR1 (MIM#203650)] and lanosterol synthase [LSS; APMR4 (MIM#618840)] are the characterized genetic factors associated with APMR. Among them, AHSG was reported in a consanguineous Iranian family and LSS gene in a Swiss origin family, while the remaining two uncharacterized loci, that is, APMR2 and APMR3, are reported in the Pakistani population. The current mini-report discusses the molecular genetics and mutational spectrum of APMR syndrome, its differential diagnosis from related disorders, and prediction of plausible candidate genes in two uncharacterized loci.

Localisation and regulation of cholesterol transporters in the human hair follicle: mapping changes across the hair cycle

Cholesterol has long been suspected of influencing hair biology, with dysregulated homeostasis implicated in several disorders of hair growth and cycling. Cholesterol transport proteins play a vital role in the control of cellular cholesterol levels and compartmentalisation. This research aimed to determine the cellular localisation, transport capability and regulatory control of cholesterol transport proteins across the hair cycle. Immunofluorescence microscopy in human hair follicle sections revealed differential expression of ATP-binding cassette (ABC) transporters across the hair cycle. Cholesterol transporter expression (ABCA1, ABCG1, ABCA5 and SCARB1) reduced as hair follicles transitioned from growth to regression. Staining for free cholesterol (filipin) revealed prominent cholesterol striations within the basement membrane of the hair bulb. Liver X receptor agonism demonstrated active regulation of ABCA1 and ABCG1, but not ABCA5 or SCARB1 in human hair follicles and primary keratinocytes. These results demonstrate the capacity of human hair follicles for cholesterol transport and trafficking. Future studies examining the role of cholesterol transport across the hair cycle may shed light on the role of lipid homeostasis in human hair disorders.

Novel mutations in Chinese hypotrichosis simplex patients associated with LSS gene

Hypotrichosis simplex (HS) is a rare form of hereditary alopecia caused by a variety of genetic mutations. Currently, only four studies regarding LSS-related HS have been reported. In this study, we try to make a definite diagnosis in two unrelated Chinese families with three pediatric patients clinically suspected of HS. Whole-exome sequencing (WES) was performed for these two families to reveal the pathogenic mutation. WES revealed two different compound heterozygous mutations in LSS in two probands that confirmed the diagnosis, including three novel mutations. In this paper, we describe a new accompanying phenotype of teeth dysplasia in a HS patient. Moreover, we provide a review of all reported LSS mutation-related patients and infer some potential genotype-phenotype correlations for the first time.

Autosomal recessive hypotrichosis with loose anagen hairs associated with TKFC mutations

BACKGROUND

Loose anagen hair is a rare form of impaired hair anchorage in which anagen hairs that lack inner and outer root sheaths can be gently and painlessly plucked from the scalp. This condition usually occurs in children and is often self-limiting. A genetic basis for the disorder has been suggested but not proven. A better understanding the aetiology of loose anagen hair may improve prevention and treatment strategies.

OBJECTIVES

To identify a possible genetic basis of loose anagen hair using next-generation DNA sequencing and functional analysis of variants identified.

METHODS

In this case study, whole-exome sequencing analysis of a pedigree with one affected individual with features of loose anagen hair was performed.

RESULTS

The patient was found to be compound heterozygous for two single-nucleotide substitutions in TKFC resulting in the following missense mutations: c.574G> C (p.Gly192Arg) and c.682C> T (p.Arg228Trp). Structural analysis of human TKFC showed that both mutations are located near the active site cavity. Kinetic assays of recombinant proteins bearing either of these amino acid substitutions showed almost no dihydroxyacetone kinase or D-glyceraldehyde kinase activity, and FMN cyclase activity reduced to just 10% of wildtype catalytic activity.

CONCLUSIONS

TKFC missense mutations may predispose to the development of loose anagen hairs. Identification of this new biochemical pathobiology expands the metabolic and genetic basis of hypotrichosis.

Mutations in SREBF1, Encoding Sterol Regulatory Element Binding Transcription Factor 1, Cause Autosomal-Dominant IFAP Syndrome

IFAP syndrome is a rare genetic disorder characterized by ichthyosis follicularis, atrichia, and photophobia. Previous research found that mutations in MBTPS2, encoding site-2-protease (S2P), underlie X-linked IFAP syndrome. The present report describes the identification via whole-exome sequencing of three heterozygous mutations in SREBF1 in 11 unrelated, ethnically diverse individuals with autosomal-dominant IFAP syndrome. SREBF1 encodes sterol regulatory element-binding protein 1 (SREBP1), which promotes the transcription of lipogenes involved in the biosynthesis of fatty acids and cholesterols. This process requires cleavage of SREBP1 by site-1-protease (S1P) and S2P and subsequent translocation into the nucleus where it binds to sterol regulatory elements (SRE). The three detected SREBF1 mutations caused substitution or deletion of residues 527, 528, and 530, which are crucial for S1P cleavage. In vitro investigation of SREBP1 variants demonstrated impaired S1P cleavage, which prohibited nuclear translocation of the transcriptionally active form of SREBP1. As a result, SREBP1 variants exhibited significantly lower transcriptional activity compared to the wild-type, as demonstrated via luciferase reporter assay. RNA sequencing of the scalp skin from IFAP-affected individuals revealed a dramatic reduction in transcript levels of low-density lipoprotein receptor (LDLR) and of keratin genes known to be expressed in the outer root sheath of hair follicles. An increased rate of in situ keratinocyte apoptosis, which might contribute to skin hyperkeratosis and hypotrichosis, was also detected in scalp samples from affected individuals. Together with previous research, the present findings suggest that SREBP signaling plays an essential role in epidermal differentiation, skin barrier formation, hair growth, and eye function.

Zebrafish models of skeletal dysplasia induced by cholesterol biosynthesis deficiency

Human disorders of the post-squalene cholesterol biosynthesis pathway frequently result in skeletal abnormalities, yet our understanding of the mechanisms involved is limited. In a forward-genetic approach, we have found that a late-onset skeletal mutant, named kolibernu7 , is the result of a cis-acting regulatory mutation leading to loss of methylsterol monooxygenase 1 (msmo1) expression within pre-hypertrophic chondrocytes. Generated msmo1nu81 knockdown mutation resulted in lethality at larval stage. We demonstrated that this is a result of both cholesterol deprivation and sterol intermediate accumulation by creating a mutation eliminating activity of Lanosterol synthase (Lss). Our results indicate that double lssnu60;msmo1nu81 and single lssnu60 mutants survive significantly longer than msmo1nu81 homozygotes. Liver-specific restoration of either Msmo1 or Lss in corresponding mutant backgrounds suppresses larval lethality. Rescued mutants develop dramatic skeletal abnormalities, with a loss of Msmo1 activity resulting in a more-severe patterning defect of a near-complete loss of hypertrophic chondrocytes marked by col10a1a expression. Our analysis suggests that hypertrophic chondrocytes depend on endogenous cholesterol synthesis, and blocking C4 demethylation exacerbates the cholesterol deficiency phenotype. Our findings offer new insight into the genetic control of bone development and provide new zebrafish models for human disorders of the cholesterol biosynthesis pathway.

Detection of a familial 21q22.3 microduplication in a fetus associated with congenital heart defects

OBJECTIVE

We present a familial 21q22.3 microduplication in a fetus associated with prenatally detected congenital heart defects (CHD).

CASE REPORT

A 38-year-old woman underwent amniocentesis at 22 weeks of gestation because of sonographic findings of double outlet of right ventricle, ventricular septal defect and transposition of great artery in the fetus. Her husband was 42 years old, and there was no CHD and congenital malformation in the family. Cytogenetic analysis revealed a karyotype of 46,XY in the fetus. Simultaneous array comparative genomic hybridization (aCGH) analysis using uncultured amniocytes revealed a 0.56-Mb microduplication of 21q22.3 or arr 21q22.3 (47,482,210-48,043,704)×3.0 [GRCh37 (hg19)] encompassing nine Online Mendelian Inheritance in Man (OMIM) genes of FTCD, SPATC1L, LSS, MCM3AP, YBEY, PCNT, DIP2A, S100B and PRMT2. aCGH analysis of the parental bloods revealed that the phenotypically normal father carried the same microduplication. The parents decided to continue the pregnancy, and a 3168-g male baby was delivered at term without Down syndrome phenotype except CHD. Mutational analysis of the CRELD1 gene on the DNA extracted from the cord blood showed no mutation in CRELD1. Postnatal molecular cytogenetic analysis of the cord blood confirmed the prenatal diagnosis. The infant underwent a successful heart surgery to correct the CHD and was doing well without psychomotor or developmental delay at six months of age.

CONCLUSION

Prenatal diagnosis of 21q22.3 microduplication associated with CHD should include a differential diagnosis of Down syndrome.

Metabolic and pathologic profiles of human LSS deficiency recapitulated in mice

Skin lesions, cataracts, and congenital anomalies have been frequently associated with inherited deficiencies in enzymes that synthesize cholesterol. Lanosterol synthase (LSS) converts (S)-2,3-epoxysqualene to lanosterol in the cholesterol biosynthesis pathway. Biallelic mutations in LSS have been reported in families with congenital cataracts and, very recently, have been reported in cases of hypotrichosis. However, it remains to be clarified whether these phenotypes are caused by LSS enzymatic deficiencies in each tissue, and disruption of LSS enzymatic activity in vivo has not yet been validated. We identified two patients with novel biallelic LSS mutations who exhibited congenital hypotrichosis and midline anomalies but did not have cataracts. We showed that the blockade of the LSS enzyme reaction occurred in the patients by measuring the (S)-2,3-epoxysqualene/lanosterol ratio in the forehead sebum, which would be a good biomarker for the diagnosis of LSS deficiency. Epidermis-specific Lss knockout mice showed neonatal lethality due to dehydration, indicating that LSS could be involved in skin barrier integrity. Tamoxifen-induced knockout of Lss in the epidermis caused hypotrichosis in adult mice. Lens-specific Lss knockout mice had cataracts. These results confirmed that LSS deficiency causes hypotrichosis and cataracts due to loss-of-function mutations in LSS in each tissue. These mouse models will lead to the elucidation of the pathophysiological mechanisms associated with disrupted LSS and to the development of therapeutic treatments for LSS deficiency.

Congenital cataract: a guide to genetic and clinical management

Worldwide 20,000-40,000 children with congenital or childhood cataract are born every year with varying degrees and patterns of lens opacification with a broad aetiology. In most cases of bilateral cataract, a causative genetic mutation can be identified, with autosomal dominant inheritance being most common in 44% of cases. Variants in genes involve lens-specific proteins or those that regulate eye development, thus giving rise to other associated ocular abnormalities. Approximately 15% of cases have systemic features, hence paediatric input is essential to minimise comorbidities and support overall development of children at high risk of visual impairment. In some metabolic conditions, congenital cataract may be the presenting sign, and therefore prompt diagnosis is important where there is an available treatment. Multidisciplinary management of children is essential, including ophthalmic surgeons, orthoptists, paediatricians, geneticists and genetic counsellors, and should extend beyond the medical team to include school and local paediatric visual support services. Early surgery and close follow up in ophthalmology is important to optimise visual potential and prevent amblyopia. Routine genetic testing is essential for the complete clinical management of patients, with next-generation sequencing of 115 genes shown to expedite molecular diagnosis, streamline care pathways and inform genetic counselling and reproductive options for the future.

Lay abstract

Childhood cataract: how to manage patients Cataract is a clouding of the lens in the eye. Cataract occurring in children has many different causes, which may include infections passed from mother to child during pregnancy, trauma, medications and exposure to radiation. In most cases of cataract occurring in both eyes, a genetic cause can be found which may be inherited from parents or occur sporadically in the developing baby itself while in the womb. Cataracts may occur on their own, with other eye conditions or be present with other disorders in the body as part of a syndrome. Genetic testing is important for all children with cataract as it can provide valuable information about cause, inheritance and risk to further children and signpost any other features of the disease in the rest of the body, permitting the assembly of the correct multidisciplinary care team. Genetic testing currently involves screening for mutations in 115 genes already known to cause cataract and has been shown to expedite diagnosis and help better manage children. Genetic counselling services can support families in understanding their diagnosis and inform future family planning. In order to optimise vision, early surgery for cataract in children is important. This is because the brain is still developing and an unobstructed pathway for light to reach the back of the eye is required for normal visual development. Any obstruction (such as cataract) if left untreated may lead to permanent sight impairment or blindness, even if it is removed later. A multidisciplinary team involved in the care of a child with cataract should include ophthalmic surgeons, orthoptists, paediatricians, geneticists and genetic counsellors, and should extend beyond the medical team to include school and local child visual support services. They will help to diagnose and manage systemic conditions, optimise vision potential and help patients and their families access best supportive care.

Basmanav FB, Mohungoo J, Pasternack-Ziach SM, Mattheisen M, Oprisoreanu AM, Humbatova A, Wolf S, Messenger A, Betz RC. Autosomal-dominant hypotrichosis with woolly hair: Novel gene locus on chromosome 4q35.1-q35.2

Hypotrichosis simplex (HS) with and without woolly hair (WH) comprises a group of rare, monogenic disorders of hair loss. Patients present with a diffuse loss of scalp and/or body hair, which usually begins in early childhood and progresses into adulthood. Some of the patients also show hair that is tightly curled. Approximately 10 genes for autosomal recessive and autosomal dominant forms of HS have been identified in the last decade, among them five genes for the dominant form. We collected blood and buccal samples from 17 individuals of a large British family with HS and WH. After having sequenced all known dominant genes for HS in this family without the identification of any disease causing mutation, we performed a genome-wide scan, using the HumanLinkage-24 BeadChip, followed by a classical linkage analysis; and whole exome-sequencing (WES). Evidence for linkage was found for a region on chromosome 4q35.1-q35.2 with a maximum LOD score of 3.61. WES led to the identification of a mutation in the gene SORBS2, encoding sorbin and SH3 domain containing 2. Unfortunately, we could not find an additional mutation in any other patient/family with HS; and in cell culture, we could not observe any difference between cloned wildtype and mutant SORBS2 using western blotting and immunofluorescence analyses. Therefore, at present, SORBS2 cannot be considered a definite disease gene for this phenotype. However, the locus on chromosome 4q is a robust and novel finding for hypotrichosis with woolly hair. Further fine mapping and sequencing efforts are therefore warranted in order to confirm SORBS2 as a plausible HS disease gene.

Cholesterol homeostasis: Links to hair follicle biology and hair disorders

Lipids and lipid metabolism are critical factors in hair follicle (HF) biology, and cholesterol has long been suspected of influencing hair growth. Altered cholesterol homeostasis is involved in the pathogenesis of primary cicatricial alopecia, mutations in a cholesterol transporter are associated with congenital hypertrichosis, and dyslipidaemia has been linked to androgenic alopecia. The underlying molecular mechanisms by which cholesterol influences pathways involved in proliferation and differentiation within HF cell populations remain largely unknown. As such, expanding our knowledge of the role for cholesterol in regulating these processes is likely to provide new leads in the development of treatments for disorders of hair growth and cycling. This review describes the current state of knowledge with respect to cholesterol homeostasis in the HF along with known and putative links to hair pathologies.