Mutations in MEOX1, encoding mesenchyme homeobox 1, cause Klippel-Feil anomaly

Isolated congenital vertebral anomaly and Sprengel's deformity in a WBP11 pathogenic variant

The pathogenic variant of WBP11 has been known as one of the various genetic causes of VACTERL syndrome. VACTERL syndrome is usually diagnosed with at least three clinical features of vertebral, heart, tracheal, esophageal, kidney, and limb anomalies. So far, only four WBP11 pathogenic variants have been documented from 13 patients, first and latest described in 2020. In this clinical report, we present a patient with an isolated vertebral anomaly and Sprengel's deformity, carrying a pathogenic variant of WBP11, representing a distinctive case of patient that has never been described before. An eight-month-old boy with a 5°-10° head tilt to the right was referred to our institution and the cervical X-ray imaging showed the vertebral anomaly. Three-dimensional (3D) volume-rendered computed tomography (CT) of the cervical spine revealed the fusion state of the right C2 and C3 facet joints. And the right shoulder appeared to be raised and right scapula elevation was identified in the 3D chest CT. In addition, whole genome sequencing presented a de novo novel WBP11 heterozygous pathogenic variant, with frameshift resulting in a loss of function. WBP11 is a cell cycle-related pleiotropic gene that encodes a pre-messenger RNA splicing factor involved in centriole duplication. Pathogenic variants in WBP11 are genetically implicated in the development of multiple congenital anomalies. Clinically, WBP11 has been previously associated with VACTERL syndrome. In this report, we document clinical manifestations, including vertebral anomalies and Sprengel's deformity. The findings presented in this report indicate that haploinsufficiency of WBP11, resulting from a heterozygous pathogenic variant, may give rise to a more diverse array of clinical phenotypes than previously documented.

Reviewing the Genetic and Molecular Foundations of Congenital Spinal Deformities: Implications for Classification and Diagnosis

Congenital spinal deformities (CSDs) are rare but severe conditions caused by abnormalities in vertebral development during embryogenesis. These deformities, including scoliosis, kyphosis, and lordosis, significantly impair patients' quality of life and present challenges in diagnosis and treatment. This review integrates genetic, molecular, and developmental insights to provide a comprehensive framework for classifying and understanding CSDs. Traditional classification systems based on morphological criteria, such as failures in vertebral formation, segmentation, or mixed defects, are evaluated alongside newer molecular-genetic approaches. Advances in genetic technologies, including whole-exome sequencing, have identified critical genes and pathways involved in somitogenesis and sclerotome differentiation, such as TBX6, DLL3, and PAX1, as well as key signaling pathways like Wnt, Notch, Hedgehog, BMP, and TGF-β. These pathways regulate vertebral development, and their disruption leads to skeletal abnormalities. The review highlights the potential of molecular classifications based on genetic mutations and developmental stage-specific defects to enhance diagnostic precision and therapeutic strategies. Early diagnosis using non-invasive prenatal testing (NIPT) and emerging tools like CRISPR-Cas9 gene editing offer promising but ethically complex avenues for intervention. Limitations in current classifications and the need for further research into epigenetic and environmental factors are discussed. This study underscores the importance of integrating molecular genetics into clinical practice to improve outcomes for patients with CSDs.

Otolaryngological Presentations of Klippel-Feil Syndrome: A Systematic Review

Klippel-Feil syndrome (KFS) is a rare congenital condition characterized by the fusion of cervical vertebrae. It classically presents with a triad of symptoms: limited cervical range of motion, a low posterior hairline, and a short neck. Common otolaryngological manifestations include hearing loss, dysphagia, cleft palate, jaw disorders, thyroid abnormalities, and ear malformations, highlighting the importance of KFS awareness in the field of otolaryngology. Recognizing these symptoms can enhance patient care and outcomes. This systematic review analyzed all case reports on KFS published in the last 10 years on PubMed. Cases were classified using the Samartzis classification, Mallampati score, and Cormack-Lehane grade. Symptoms were then identified, and common imaging techniques were noted to provide clinical recommendations for treating KFS patients. The study found that more severe vertebral fusions are linked to more serious symptoms. Otolaryngologists should consider KFS in their differential diagnosis, especially in patients presenting with neck masses and pain, hearing loss, dysphagia, scoliosis, Sprengel's deformity, or other musculoskeletal abnormalities.

Cardiovascular Findings in Klippel-Feil Syndrome: A Systematic Review

Klippel-Feil syndrome (KFS) is a congenital disease defined by an abnormal fusion between cervical vertebrae. Due to the rarity of the disorder, its prevalence, along with its pathogenesis and associated conditions, remains to be clearly defined. The aim of this review is to summarize the findings of all case reports of KFS in PubMed over the last 10 years that describe cardiovascular disease, defects, or abnormalities. A total of 43 articles containing 46 reports were included from the 157 case reports considered. Cases were reviewed for commonality in biological sex and vertebral fusion and level using the Samartzis classification system to determine what association, if any, exists with the cardiovascular findings analyzed. A total of 72% of cases reported one or more findings consistent with congenital heart disease. Using the Samartzis classification system, type III KFS was the most common fusion profile overall in this subset of patients. The heterogeneity of disease manifestations makes the treatment and management of KFS case-dependent, though current guidelines highlight the importance of a multidisciplinary care team for pediatric patients. Our findings support this notion and provide evidence for the inclusion of a care provider who specializes in cardiovascular medicine in patients of all ages, as well as the consideration of additional diagnostic screening exams for cardiovascular abnormalities. Future studies into the embryological origin of KFS and a more robust search for a genetic marker are needed to better understand the development of the disease and its various associated conditions.

Cellular and molecular control of vertebrate somitogenesis

Segmentation is a fundamental feature of the vertebrate body plan. This metameric organization is first implemented by somitogenesis in the early embryo, when paired epithelial blocks called somites are rhythmically formed to flank the neural tube. Recent advances in in vitro models have offered new opportunities to elucidate the mechanisms that underlie somitogenesis. Notably, models derived from human pluripotent stem cells introduced an efficient proxy for studying this process during human development. In this Review, we summarize the current understanding of somitogenesis gained from both in vivo studies and in vitro studies. We deconstruct the spatiotemporal dynamics of somitogenesis into four distinct modules: dynamic events in the presomitic mesoderm, segmental determination, somite anteroposterior polarity patterning, and epithelial morphogenesis. We first focus on the segmentation clock, as well as signalling and metabolic gradients along the tissue, before discussing the clock and wavefront and other models that account for segmental determination. We then detail the molecular and cellular mechanisms of anteroposterior polarity patterning and somite epithelialization.

Regulatory Role of Meox1 in Muscle Growth of Sebastes schlegelii

Meox1 is a critical transcription factor that plays a pivotal role in embryogenesis and muscle development. It has been established as a marker gene for growth-specific muscle stem cells in zebrafish. In this study, we identified the SsMeox1 gene in a large teleost fish, Sebastes schlegelii. Through in situ hybridization and histological analysis, we discovered that SsMeox1 can be employed as a specific marker of growth-specific muscle stem cells, which originate from the somite stage and are primarily situated in the external cell layer (ECL) and myosepta, with a minor population distributed among muscle fibers. The knockdown of SsMeox1 resulted in a significant increase in Ccnb1 expression, subsequently promoting cell cycle progression and potentially accelerating the depletion of the stem cell pool, which ultimately led to significant growth retardation. These findings suggest that SsMeox1 arrests the cell cycle of growth-specific muscle stem cells in the G2 phase by suppressing Ccnb1 expression, which is essential for maintaining the stability of the growth-specific muscle stem cell pool. Our study provides significant insights into the molecular mechanisms underlying the indeterminate growth of large teleosts.

Whole-Exome Sequencing Analysis Identifies Risk Genes in Atlantoaxial Dislocation Patients with Sandwich Fusion

Sandwich fusion of Klippel-Feil syndrome (KFS), which is a rare congenital disorder involving the fusion of cervical vertebrae, poses significant challenges in the diagnosis and treatment of atlantoaxial dislocation (AAD). While the disorder's genetic basis is not well-understood, the rarity of the sandwich fusion makes it difficult to study. Whole-exome sequencing (WES) was conducted on 68 unrelated Chinese patients with sandwich fusion. The study compared their genetic data with a control group of 219 individuals without musculoskeletal disorders. Various analyses, including mutational burden assessments, were employed to identify potential pathogenic genes. The study identified significant genetic variations in patients with sandwich fusion, highlighting genes like KMT5A, HYDIN, and PCDHB4 as potential contributors. Notably, severe cases exhibited oligogenic effects, with mutations in genes like MEOX1 associated with the severity of spinal issues. These findings offer critical insights into the genetic basis of sandwich fusion and provide a foundation for future research and therapeutic development.

Molecular landscape of congenital vertebral malformations: recent discoveries and future directions

Vertebral malformations (VMs) pose a significant global health problem, causing chronic pain and disability. Vertebral defects occur as isolated conditions or within the spectrum of various congenital disorders, such as Klippel-Feil syndrome, congenital scoliosis, spondylocostal dysostosis, sacral agenesis, and neural tube defects. Although both genetic abnormalities and environmental factors can contribute to abnormal vertebral development, our knowledge on molecular mechanisms of numerous VMs is still limited. Furthermore, there is a lack of resource that consolidates the current knowledge in this field. In this pioneering review, we provide a comprehensive analysis of the latest research on the molecular basis of VMs and the association of the VMs-related causative genes with bone developmental signaling pathways. Our study identifies 118 genes linked to VMs, with 98 genes involved in biological pathways crucial for the formation of the vertebral column. Overall, the review summarizes the current knowledge on VM genetics, and provides new insights into potential involvement of biological pathways in VM pathogenesis. We also present an overview of available data regarding the role of epigenetic and environmental factors in VMs. We identify areas where knowledge is lacking, such as precise molecular mechanisms in which specific genes contribute to the development of VMs. Finally, we propose future research avenues that could address knowledge gaps.

Identification of the novel FOXP3-dependent Treg cell transcription factor MEOX1 by high-dimensional analysis of human CD4+ T cells

CD4+ T cells play a central role in the adaptive immune response through their capacity to activate, support and control other immune cells. Although these cells have become the focus of intense research, a comprehensive understanding of the underlying regulatory networks that orchestrate CD4+ T cell function and activation is still incomplete. Here, we analyzed a large transcriptomic dataset consisting of 48 different human CD4+ T cell conditions. By performing reverse network engineering, we identified six common denominators of CD4+ T cell functionality (CREB1, E2F3, AHR, STAT1, NFAT5 and NFATC3). Moreover, we also analyzed condition-specific genes which led us to the identification of the transcription factor MEOX1 in Treg cells. Expression of MEOX1 was comparable to FOXP3 in Treg cells and can be upregulated by IL-2. Epigenetic analyses revealed a permissive epigenetic landscape for MEOX1 solely in Treg cells. Knockdown of MEOX1 in Treg cells revealed a profound impact on downstream gene expression programs and Treg cell suppressive capacity. These findings in the context of CD4+ T cells contribute to a better understanding of the transcriptional networks and biological mechanisms controlling CD4+ T cell functionality, which opens new avenues for future therapeutic strategies.

Examining craniofacial variation among crispant and mutant zebrafish models of human skeletal diseases

Genetic diseases affecting the skeletal system present with a wide range of symptoms that make diagnosis and treatment difficult. Genome-wide association and sequencing studies have identified genes linked to human skeletal diseases. Gene editing of zebrafish models allows researchers to further examine the link between genotype and phenotype, with the long-term goal of improving diagnosis and treatment. While current automated tools enable rapid and in-depth phenotyping of the axial skeleton, characterizing the effects of mutations on the craniofacial skeleton has been more challenging. The objective of this study was to evaluate a semi-automated screening tool can be used to quantify craniofacial variations in zebrafish models using four genes that have been associated with human skeletal diseases (meox1, plod2, sost, and wnt16) as test cases. We used traditional landmarks to ground truth our dataset and pseudolandmarks to quantify variation across the 3D cranial skeleton between the groups (somatic crispant, germline mutant, and control fish). The proposed pipeline identified variation between the crispant or mutant fish and control fish for four genes. Variation in phenotypes parallel human craniofacial symptoms for two of the four genes tested. This study demonstrates the potential as well as the limitations of our pipeline as a screening tool to examine multi-dimensional phenotypes associated with the zebrafish craniofacial skeleton.

The role of MEOX1 in non-neoplastic and neoplastic diseases

Targeted gene therapy has shown durable efficacy in non-neoplastic and neoplastic patients. Therefore, finding a suitable target has become a key area of research. Mesenchyme homeobox 1 (MEOX1) is a transcriptional factor that plays a significant role in regulation of somite development. Evidence indicates that abnormalities in MEOX1 expression and function are associated with a variety of pathologies, including non-neoplastic and neoplastic diseases. MEOX1 expression is upregulated during progression of most diseases and plays a critical role in maintenance of the cellular phenotypes such as cell differentiation, cell cycle arrest and senescence, migration, and proliferation. Therefore, MEOX1 may become an important molecular target and therapeutic target. This review will discuss the current state of knowledge on the role of MEOX1 in different diseases.

Multimodal single-cell profiling of intrahepatic cholangiocarcinoma defines hyperactivated Tregs as a potential therapeutic target

BACKGROUND & AIMS

The landscape and function of the immune infiltrate of intrahepatic cholangiocarcinoma (iCCA), a rare, yet aggressive tumor of the biliary tract, remains poorly characterized, limiting development of successful immunotherapies. Herein, we aimed to define the molecular characteristics of tumor-infiltrating leukocytes with a special focus on CD4+ regulatory T cells (Tregs).

METHODS

We used high-dimensional single-cell technologies to characterize the T-cell and myeloid compartments of iCCA tissues, comparing these with their tumor-free peritumoral and circulating counterparts. We further used genomics and cellular assays to define the iCCA-specific role of a novel transcription factor, mesenchyme homeobox 1 (MEOX1), in Treg biology.

RESULTS

We found poor infiltration of putative tumor-specific CD39+ CD8+ T cells accompanied by abundant infiltration of hyperactivated CD4+ Tregs. Single-cell RNA-sequencing identified an altered network of transcription factors in iCCA-infiltrating compared to peritumoral T cells, suggesting reduced effector functions by tumor-infiltrating CD8+ T cells and enhanced immunosuppression by CD4+ Tregs. Specifically, we found that expression of MEOX1 was highly enriched in tumor-infiltrating Tregs, and demonstrated that MEOX1 overexpression is sufficient to reprogram circulating Tregs to acquire the transcriptional and epigenetic landscape of tumor-infiltrating Tregs. Accordingly, enrichment of the MEOX1-dependent gene program in Tregs was strongly associated with poor prognosis in a large cohort of patients with iCCA.

CONCLUSIONS

We observed abundant infiltration of hyperactivated CD4+ Tregs in iCCA tumors along with reduced CD8+ T-cell effector functions. Interfering with hyperactivated Tregs should be explored as an approach to enhance antitumor immunity in iCCA.

LAY SUMMARY

Immune cells have the potential to slow or halt the progression of tumors. However, some tumors, such as intrahepatic cholangiocarcinoma, are associated with very limited immune responses (and infiltration of cancer-targeting immune cells). Herein, we show that a specific population of regulatory T cells (a type of immune cell that actually suppresses the immune response) are hyperactivated in intrahepatic cholangiocarcinoma. Targeting these cells could enable cancer-targeting immune cells to act more effectively and should be looked at as a potential therapeutic approach to this aggressive cancer type.

The squiggle tail (squig) mutation in mice is associated with a deletion in the mesenchyme homeobox 1 (Meox1) gene

Objective

We have taken a positional approach to assign the spontaneous squiggle tail (squig) mutation in mice to a specific gene defect.

Results

A large panel of backcross mice was produced and characterized to map squig to high genetic resolution on mouse Chromosome (Chr) 11. Two overlapping candidate genes that co-localized with squig (Meox1, for mesenchyme homeobox 1; and Gm11551, which encodes a lncRNA located entirely within the first intron of Meox1) were fully sequenced to discover any squig-specific defects. This analysis revealed a 3195 bp deletion that includes all of Meox1, Exon 1 but does not disrupt Gm11551. We recommend that the squig mutation be renamed Meox1^squig, and suggest that this variant may offer an appropriate animal model for Klippel-Feil syndrome 2 (KFS2) in humans.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13104-022-06192-z.

Klippel-Feil Syndrome: morphological findings in a 19th-century musealized skull from Viana del Bollo (Orense, Spain)

The aim of this study is to show the cranial alterations that Klippel-Feil syndrome produced in a case older than 200 years. Few paleopathological case studies diagnosed as Klippel-Feil Syndrome are focused on cranial abnormalities. A skull numbered 778, belonging to the Federico Olóriz Aguilera collection (Spain, 19th century AD), Universidad Complutense de Madrid, belonging to a young man born in a town in the North of Spain, was investigated. This cranium was visually inspected, hence macroscopically and paleoradiologically studied, using the images obtained through conventional radiology and CT scan imaging. In addition to the vertebral fusion between the atlas (C1) and the axis (C2), atlanto-occipital fusion, basilar impression, obliteration of the sagittal suture, enlarged parietal foramina and significant craniofacial asymmetry affecting maxillary bones, sphenoid, orbits, nasal bones and both palatines were observed. Morphological findings make it possible to diagnose a Klippel-Feil syndrome, possibly type-II, although the lack of the rest of the spinal column renders it impossible to verify other spinal anomalies. As a limitation, only the cranium and two cervical vertebrae were preserved, hence the possible involvement of the rest of the skeleton cannot be verified.

Human follicular mites: Ectoparasites becoming symbionts

Most humans carry mites in the hair follicles of their skin for their entire lives. Follicular mites are the only metazoans tha continuously live on humans. We propose that Demodex folliculorum (Acari) represents a transitional stage from a host-injuring obligate parasite to an obligate symbiont. Here, we describe the profound impact of this transition on the genome and physiology of the mite. Genome sequencing revealed that the permanent host association of D. folliculorum led to an extensive genome reduction through relaxed selection and genetic drift, resulting in the smallest number of protein-coding genes yet identified among panarthropods. Confocal microscopy revealed that this gene loss coincided with an extreme reduction in the number of cells. Single uninucleate muscle cells are sufficient to operate each of the three segments that form each walking leg. While it has been assumed that the reduction of the cell number in parasites starts early in development, we identified a greater total number of cells in the last developmental stage (nymph) than in the terminal adult stage, suggesting that reduction starts at the adult or ultimate stage of development. This is the first evolutionary step in an arthropod species adopting a reductive, parasitic or endosymbiotic lifestyle. Somatic nuclei show underreplication at the diploid stage. Novel eye structures or photoreceptors as well as a unique human host melatonin-guided day/night rhythm are proposed for the first time. The loss of DNA repair genes coupled with extreme endogamy might have set this mite species on an evolutionary dead-end trajectory.

Dynamics of muscle growth and regeneration: Lessons from the teleost

The processes of myogenesis during both development and regeneration share a number of similarities across both amniotes and teleosts. In amniotes, the process of muscle formation is considered largely biphasic, with developmental myogenesis occurring through hyperplastic fibre deposition and postnatal muscle growth driven through hypertrophy of existing fibres. In contrast, teleosts continue generating new muscle fibres during adult myogenesis through a process of eternal hyperplasia using a dedicated stem cell system termed the external cell layer. During developmental and regenerative myogenesis alike, muscle progenitors interact with their niche to receive cues guiding their transition into myoblasts and ultimately mature myofibres. During development, muscle precursors receive input from neighbouring embryological tissues; however, during repair, this role is fulfilled by other injury resident cell types, such as those of the innate immune response. Recent work has focused on the role of macrophages as a pro-regenerative cell type which provides input to muscle satellite cells during regenerative myogenesis. As zebrafish harbour a satellite cell system analogous to that of mammals, the processes of regeneration can be interrogated in vivo with the imaging intensive approaches afforded in the zebrafish system. This review discusses the strengths of zebrafish with a focus on both the similarities and differences to amniote myogenesis during both development and repair.

Whole-genome sequencing of brown-marbled grouper (Epinephelus fuscoguttatus) provides insights into adaptive evolution and growth differences

The brown-marbled grouper (Epinephelus fuscoguttatus) is an important species of fish in the coral reef ecosystem and marine aquaculture industry. In this study, a high-quality chromosome-level genome of brown-marbled grouper was assembled using Oxford Nanopore technology and Hi-C technology. The GC content and heterozygosity were approximately 42% and 0.35%, respectively. A total of 230 contigs with a total length of 1047 Mb and contig N50 of 13.8 Mb were assembled, and 228 contigs (99.13%) were anchored into 24 chromosomes. A total of 24,005 protein-coding genes were predicted, among which 23,862 (99.4%) predicted genes were annotated. Phylogenetic analysis showed that brown-marbled grouper and humpback grouper were clustered into one clade that separated approximately 11-23 million years ago. Collinearity analyses showed that there was no obvious duplication of large fragments between chromosomes in the brown-marbled grouper. Genomes of the humpback grouper and giant grouper showed a high collinearity with that of the brown-marbled grouper. A total of 305 expanded gene families were detected in the brown-marbled grouper genome, which is mainly involved in disease resistance. In addition, a genetic linkage map with 3061.88 cM was constructed. Based on the physical and genetic map, one growth-related quantitative trait loci was detected in 32,332,447 bp of chromosome 20, and meox1 and etv4 were considered candidate growth-related genes. This study provides pivotal genetic resources for further evolutionary analyses and artificial breeding of groupers.

Establishment of a developmental neurotoxicity test by Sox1-GFP mouse embryonic stem cells

Developmental toxicity tests have been generated by applying the embryonic stem cell tests at the European Centre for the Validation of Alternative Methods, or by using the embryoid body test in our laboratory. This study was undertaken to explore novel developmental neurotoxicity (DNT) assay, using a Sox1-GFP cell line (mouse embryonic stem cells with an endogenous Sox1-GFP reporter). The expression of Sox1, a marker for neuroepithelial cells, is detected by green fluorescence, and the fluorescence intensity is a critical factor for achieving neuronal differentiation. Sox1-GFP cells cultured for 24 h were exposed to eleven neurotoxicants and four non-neurotoxicants. CCK-8 assays were performed to determine IC₅₀ values after 48 h of chemical treatment. The fluorescence intensity of GFP was measured 4 days after treating the cells, and it was observed to decrease after exposure to neurotoxicants at higher concentrations, thereby indicating that the neuronal differentiation of Sox1-GFP cells is inhibited by the chemicals. Taken together, the results obtained in this study provide a model for DNT using embryonic stem cells, which may be applied to evaluate the toxicity of new chemicals or new drug candidates.

Rare association of Klippel-Feil syndrome with situs inversus totalis and review of the genetic background

Klippel-Feil syndrome (KFS) is a rare congenital anomaly in forming the cervical vertebrae resulting in the fusion of two or more of the vertebrae. KFS is associated with many congenital anomalies, some of which are common and well known. Here, we report a child with an extremely rare association of KFS with situs inversus totalis (SIT). Both KFS and SIT are genetically heterogeneous and their co-occurrence suggests a high possibility of sharing the same underlying causative agent. Here, we review the genetic background that is known for these two conditions in the literature.

Characterising open chromatin in chick embryos identifies cis-regulatory elements important for paraxial mesoderm formation and axis extension

Somites arising from paraxial mesoderm are a hallmark of the segmented vertebrate body plan. They form sequentially during axis extension and generate musculoskeletal cell lineages. How paraxial mesoderm becomes regionalised along the axis and how this correlates with dynamic changes of chromatin accessibility and the transcriptome remains unknown. Here, we report a spatiotemporal series of ATAC-seq and RNA-seq along the chick embryonic axis. Footprint analysis shows differential coverage of binding sites for several key transcription factors, including CDX2, LEF1 and members of HOX clusters. Associating accessible chromatin with nearby expressed genes identifies cis-regulatory elements (CRE) for TCF15 and MEOX1. We determine their spatiotemporal activity and evolutionary conservation in Xenopus and human. Epigenome silencing of endogenous CREs disrupts TCF15 and MEOX1 gene expression and recapitulates phenotypic abnormalities of anterior-posterior axis extension. Our integrated approach allows dissection of paraxial mesoderm regulatory circuits in vivo and has implications for investigating gene regulatory networks.

Comparative proteomics analysis for identifying the lipid metabolism related pathways in patients with Klippel-Feil syndrome

Background

Klippel-Feil syndrome (KFS) represents the rare and complex deformity characterized by congenital defects in the formation or segmentation of the cervical vertebrae. There is a wide gap in understanding the detailed mechanisms of KFS because of its rarity, heterogeneity, small pedigrees, and the broad spectrum of anomalies.

Methods

We recruited eight patients of Chinese Han ethnicity with KFS, five patients with congenital scoliosis (CS) who presented with congenital fusion of the thoracic or lumbar spine and without known syndrome or cervical deformity, and seven healthy controls. Proteomic analysis by data-independent acquisition (DIA) was performed to identify the differential proteome among the three matched groups and the data were analyzed by bioinformatics tools including Gene Ontology (GO) categories and Ingenuity Pathway Analysis (IPA) database, to explore differentially abundant proteins (DAPs) and canonical pathways involved in the pathogenesis of KFS.

Results

A total of 49 DAPs were detected between KFS patients and the controls, and moreover, 192 DAPs were identified between patients with KFS and patients with CS. Fifteen DAPs that were common in both comparisons were considered as candidate biomarkers for KFS, including membrane primary amine oxidase, noelin, galectin-3-binding protein, cadherin-5, glyceraldehyde-3-phosphate dehydrogenase, peroxiredoxin-1, CD109 antigen, and eight immunoglobulins. Furthermore, the same significant canonical pathways of LXR/RXR activation and FXR/RXR activation were observed in both comparisons. Seven of DAPs were apolipoproteins related to these pathways that are involved in lipid metabolism.

Conclusions

This study provides the first proteomic profile for understanding the pathogenesis and identifying predictive biomarkers of KFS. We detected 15 DAPs that were common in both comparisons as candidate predictive biomarkers of KFS. The lipid metabolism-related canonical pathways of LXR/RXR and FXR/RXR activation together with seven differentially abundant apolipoproteins may play significant roles in the etiology of KFS and provide possible pathogenesis correlation between KFS and CS.

Further delineation of MYO18B-related autosomal recessive Klippel-Feil syndrome with myopathy and facial dysmorphism

Klippel-Feil syndrome 4 (KFS4; MIM# 616549) is an autosomal recessive disorder caused by biallelic pathogenic variants in MYO18B and comprises, in addition to Klippel-Feil anomaly (KFA), nemaline myopathy, facial dysmorphism, and short stature. We aim to outline the natural history of KFS4 and provide an updated description of its clinical, radiological, laboratory, and molecular findings. We comprehensively analyzed the medical records of 6 Saudi and 1 American patients (including 5 previously unpublished cases) with a molecularly confirmed diagnosis of KFS4. All patients had myopathy of varying severity that followed a slowly progressive or non-progressive course, affecting primarily the proximal musculature of the lower limb although hand involvement with distal arthrogryposis and abnormal interphalangeal creases was also observed. KFA and characteristic dysmorphic features, including ptosis and bulbous nose, were observed in all but two patients. The causal MYO18B variants were a founder NM_032608.5:c.6905C>A; p.(Ser2302*) variant in the Saudi patients (P1-P6) and a novel MYO18B homozygous variant (c.6660_6670del;p.[Arg2220Serfs*74]) in the American Caucasian patient (P7). We report the phenotypic and genetic findings in seven patients with KFS4. We describe the natural history of this disease, confirm myopathy as a universal feature and describe its pattern and progression, and note interesting differences between the phenotypes observed in patients with KFA and those without.

Genetics and signaling mechanisms of orofacial clefts

Craniofacial development involves several complex tissue movements including several fusion processes to form the frontonasal and maxillary structures, including the upper lip and palate. Each of these movements are controlled by many different factors that are tightly regulated by several integral morphogenetic signaling pathways. Subject to both genetic and environmental influences, interruption at nearly any stage can disrupt lip, nasal, or palate fusion and result in a cleft. Here, we discuss many of the genetic risk factors that may contribute to the presentation of orofacial clefts in patients, and several of the key signaling pathways and underlying cellular mechanisms that control lip and palate formation, as identified primarily through investigating equivalent processes in animal models, are examined.

Congenital Fusion of Dens to T3 Vertebra in Klippel-Feil Syndrome

BACKGROUND

Patients with Klippel-Feil syndrome may present with neurologic complaints such as neck pain, radiculopathy and gait instability. Here we describe surgical management of a patient with congenital fusion of the occipital-cervical region and also block circumferential fusion of dens to T3 with spinal cord compression. This report is the first of its kind with such extensive fusion.

CASE DESCRIPTION

Our patient was a 56 year-old female, who presented with neck pain and tingling in all extremities. On exam, she had a short neck, prominent jaw with extremely limited range of motion in neck and features of myelopathy. CT showed fusion of the dens to T3 vertebrae. Patient underwent sub-occipital craniectomy, C1 laminectomy and Occiput to T5 posterior fixation and fusion with neurologic improvement.

CONCLUSION

This is the first reported case of Klippel-Feil syndrome with fusion of all cervical vertebrae down to T3. We recommend surgery for advanced cases of myelopathy or radiculopathy due to stenosis and spinal instability.

Atlas assimilation: spectrum of associated radiographic abnormalities, clinical presentation, and management in children below 10 years

OBJECTIVE

To analyze the varied presentation and management of atlas assimilation with associated radiographic abnormalities in children in the MRI era METHODS: Database analysis of 313 children (less than 10 years) RESULTS: Atlas assimilation (AA) was associated with atlantoaxial dislocation in 12, abnormal skull base and Chiari I abnormality in 42, C2-C3 segmentation failure and instability and Chiari I abnormality in 74, and condylar hypoplasia and basilar invagination in 74. Proatlas segmentation failures were 54, atlantoaxial rotary dislocation in 26 with Goldenhar's syndrome, abnormal C1 atlas posterior arch causing dynamic compression of cord in 31 children. Vascular compromise was documented in 26 children. The study encompassed ages 6 months to 10 years. Cranial nerves commonly affected were glossopharyngeal, vagal, and hypoglossal nerves. Children below 2 years presented with torticollis, failure to thrive, difficulty swallowing, and motor and sensory deficits. Craniovertebral junction instability associated with AA was treated with custom-built craniocervical orthosis below 5 years. Closed reduction of instability or basilar invagination was attempted with neuromuscular blockade under anesthesia and traction above age 5 years. Successful reduction was treated with dorsal foramen magnum and atlas decompression with occiput-C2 dorsal fusion using rib grafts below the age of 5 years and instrumentation after that. Follow-up was 2 to 32 years. Neurological recovery was seen in nearly all patients.

CONCLUSIONS

Children with atlas assimilation and associated abnormalities may be symptomatic in early childhood. The treatment depends on the age and tailored to the abnormalities present. The long-term results have been successful.

The mutational burden and oligogenic inheritance in Klippel-Feil syndrome

Background

Klippel-Feil syndrome (KFS) represents a rare anomaly characterized by congenital fusion of the cervical vertebrae. The underlying molecular etiology remains largely unknown because of the genetic and phenotypic heterogeneity.

Methods

We consecutively recruited a Chinese cohort of 37 patients with KFS. The clinical manifestations and radiological assessments were analyzed and whole-exome sequencing (WES) was performed. Additionally, rare variants in KFS cases and controls were compared using genetic burden analysis.

Results

We primarily examined rare variants in five reported genes (GDF6, MEOX1, GDF3, MYO18B and RIPPLY2) associated with KFS and detected three variants of uncertain significance in MYO18B. Based on rare variant burden analysis of 96 candidate genes related to vertebral segmentation defects, we identified BAZ1B as having the highest probability of association with KFS, followed by FREM2, SUFU, VANGL1 and KMT2D. In addition, seven patients were proposed to show potential oligogenic inheritance involving more than one variants in candidate genes, the frequency of which was significantly higher than that in the in-house controls.

Conclusions

Our study presents an exome-sequenced cohort and identifies five novel genes potentially associated with KFS, extending the spectrum of known mutations contributing to this syndrome. Furthermore, the genetic burden analysis provides further evidence for potential oligogenic inheritance of KFS.

Genetic and phenotypic characterization of NKX6-2-related spastic ataxia and hypomyelination

Background and purpose

Hypomyelinating leukodystrophies are a heterogeneous group of genetic disorders with a wide spectrum of phenotypes and a high rate of genetically unsolved cases. Bi‐allelic mutations in NKX6‐2 were recently linked to spastic ataxia 8 with hypomyelinating leukodystrophy.

Methods

Using a combination of homozygosity mapping, exome sequencing, and detailed clinical and neuroimaging assessment a series of new NKX6‐2 mutations in a multicentre setting is described. Then, all reported NKX6‐2 mutations and those identified in this study were combined and an in‐depth analysis of NKX6‐2‐related disease spectrum was provided.

Results

Eleven new cases from eight families of different ethnic backgrounds carrying compound heterozygous and homozygous pathogenic variants in NKX6‐2 were identified, evidencing a high NKX6‐2 mutation burden in the hypomyelinating leukodystrophy disease spectrum. Our data reveal a phenotype spectrum with neonatal onset, global psychomotor delay and worse prognosis at the severe end and a childhood onset with mainly motor phenotype at the milder end. The phenotypic and neuroimaging expression in NKX6‐2 is described and it is shown that phenotypes with epilepsy in the absence of overt hypomyelination and diffuse hypomyelination without seizures can occur.

Conclusions

NKX6‐2 mutations should be considered in patients with autosomal recessive, very early onset of nystagmus, cerebellar ataxia with hypotonia that rapidly progresses to spasticity, particularly when associated with neuroimaging signs of hypomyelination. Therefore, it is recommended that NXK6‐2 should be included in hypomyelinating leukodystrophy and spastic ataxia diagnostic panels.

Expanding the clinical history associated with syndromic Klippel-Feil: A unique case of comorbidity with medulloblastoma

Klippel-Feil syndrome (KFS) is an exceedingly rare constitutional disorder in which a paucity of knowledge exists about the disease and its associated morbidity and mortality. We present a 4-year-old male with KFS, who notably was also diagnosed with large-cell anaplastic medulloblastoma. We evaluated the genetic basis of co-occurring KFS and medulloblastoma and the role of MYO18B as related to medulloblastoma. Constitutional and somatic variant and copy number analyses were performed from DNA-based exome studies, along with RNA-sequencing of tumor tissue, to elucidate the genetic etiology of the co-existing disease states. We identified novel constitutional compound heterozygous frameshift variants (NM_032608.5: p.Leu2257SerfsTer16 and p.Arg2220SerfsTer74) each encoding a premature stop of translation in MYO18B, consistent with a diagnosis of KFS. We did not identify any somatic variants of known relevance or disease-relevant therapeutic targets in the tumor. The somatic copy number profile was suggestive of Group 3γ medulloblastoma. Relative to pediatric brain tumors, medulloblastoma, particularly, Group 3, had increased gene expression of MYO18B. In summary, coexisting constitutional and somatic diagnoses in this patient enabled the elucidation of the genetic etiology of KFS and provided support for the role of MYO18B in tumor suppression.

Meox1 accelerates myocardial hypertrophic decompensation through Gata4

Aims

Pathological hypertrophy is the result of gene network regulation, which ultimately leads to adverse cardiac remodelling and heart failure (HF) and is accompanied by the reactivation of a 'foetal gene programme'. The Mesenchyme homeobox 1 (Meox1) gene is one of the foetal programme genes. Meox1 may play a role in embryonic development, but its regulation of pathological hypertrophy is not known. Therefore, this study investigated the effect of Meox1 on pathological hypertrophy, including familial and pressure overload-induced hypertrophy, and its potential mechanism of action.

Methods and results

Meox1 expression was markedly down-regulated in the wild-type adult mouse heart with age, and expression was up-regulated in heart tissues from familial dilated cardiomyopathy (FDCM) mice of the cTnTR141W strain, familial hypertrophic cardiomyopathy (FHCM) mice of the cTnTR92Q strain, pressure overload-induced HF mice, and hypertrophic cardiomyopathy (HCM) patients. Echocardiography, histopathology, and hypertrophic molecular markers consistently demonstrated that Meox1 overexpression exacerbated the phenotypes in FHCM and in mice with thoracic aorta constriction (TAC), and that Meox1 knockdown improved the pathological changes. Gata4 was identified as a potential downstream target of Meox1 using digital gene expression (DGE) profiling, real-time PCR, and bioinformatics analysis. Promoter activity data and chromatin immunoprecipitation (ChIP) and Gata4 knockdown analyses indicated that Meox1 acted via activation of Gata4 transcription.

Conclusion

Meox1 accelerated decompensation via the downstream target Gata4, at least in part directly. Meox1 and other foetal programme genes form a highly interconnected network, which offers multiple therapeutic entry points to dampen the aberrant expression of foetal genes and pathological hypertrophy.

MEOX1 Promotes Tumor Progression and Predicts Poor Prognosis in Human Non-Small-Cell Lung Cancer

Background: MEOX1 is a homeobox transcriptional factor, and plays essential roles in regulating somite development. Our previous study indicated that MEOX1 is a critical molecular target in mesenchymal-like cancer cells in PTEN-deficient Trastuzumab resistant breast cancer. Despite the potential implication of MEOX1 for the cancer progression, no previous studies examined its level and clinical significance in lung cancer tissues. In this study, we aimed to detect the MEOX1 expression and correlate its level with clinical outcome in non-small-cell lung cancer patients (NSCLC). Methods: MEOX1 gene expression in lung cancer was examined by using the Oncomine database. MEOX1 protein levels were evaluated by IHC using the corresponding primary antibody on two different commercial lung cancer tissue arrays. siRNA knockdown was used to elucidate the function of MEOX1. Results: Analysis of the Oncomine datasets identified that an elevation of MEOX1 in gene amplification in lung cancer tissues in comparison to normal lung tissues. Immunohistochemistical analysis demonstrated that MEOX1 was localized predominantly in the nucleus, and positive rate was 67.3% (111/165) in NSCLC samples. Statistical analysis revealed high levels of MEOX1 significantly correlated with Lymph Node Metastasis and Stage. Kaplan-Meier survival analysis showed that high levels of MEOX1 were significantly associated with unfavorable survival in NSCLC patients, and MEOX1 nucleus staining had worse survival, than did patients with overall expression in lung squamous cell carcinoma patients. Multivariate Cox's regression analysis found that MEOX1 was an independent poor prognostic predictor for patients with NSCLC. Silencing of MEOX1 by specific SiRNA significantly inhibited H460 and H1299 cell proliferation and sphere formation in serum-free medium. Conclusions: Our results firstly indentified that high levels of MEOX1 especially nuclear staining was an independent prognostic factor for NSCLC, and it served a essential roles in the regulation of cell proliferation and colony formation in vitro. It may represent a potential target for the NSCLC treatment.

Klippel-Feil: A constellation of diagnoses, a contemporary presentation, and recent national trends

Background:

Klippel–Feil syndrome (KFS) includes craniocervical anomalies, low posterior hairline, and brevicollis, with limited cervical range of motion; however, there remains no consensus on inheritance pattern. This study defines incidence, characterizes concurrent diagnoses, and examines trends in the presentation and management of KFS.

Methods:

This was a retrospective review of the Kid's Inpatient Database (KID) for KFSpatients aged 0–20 years from 2003 to 2012. Incidence was established using KID-supplied year and hospital-trend weights. Demographics and secondary diagnoses associated with KFS were evaluated. Comorbidities, anomalies, and procedure type trends from 2003 to 2012 were assessed for likelihood to increase among the years studied using ANOVA tests.

Results:

Eight hundred and fifty-eight KFS diagnoses (age: 9.49 years; 51.1% females) and 475 patients with congenital fusion (CF) (age: 8.33 years; 50.3% females) were analyzed. We identified an incidence rate of 1/21,587 discharges. Only 6.36% of KFS patients were diagnosed with Sprengel's deformity; 1.44% with congenital fusion. About 19.1% of KFS patients presented with another spinal abnormality and 34.0% presented with another neuromuscular anomaly. About 36.51% of KFS patients were diagnosed with a nonspinal or nonmusculoskeletal anomaly, with the most prevalent anomalies being of cardiac origin (12.95%). About 7.34% of KFS patients underwent anterior fusions, whereas 6.64% of KFS patients underwent posterior fusions. The average number of levels operated on was 4.99 with 8.28% receiving decompressions. Interbody devices were used in 2.45% of cases. The rate of fusions with <3 levels (7.46%) was comparable to that of 3 levels or greater (7.81%).

Conclusions:

KFS patients were more likely to have other spinal abnormalities (19.1%) and nonnervous system abnormalities (13.63%). Compared to congenital fusions, KFS patients were more likely to have congenital abnormalities such as Sprengel's deformity. KFS patients are increasingly being treated with spinal fusion.

Level of Evidence:

III

A Novel 12q13.2-q13.3 Microdeletion Syndrome With Combined Features of Diamond Blackfan Anemia, Pierre Robin Sequence and Klippel Feil Deformity

Diamond-Blackfan anemia (DBA) is a rare congenital erythroid aplasia with a highly heterogeneous genetic background; it usually occurs in infancy. Approximately 30–40% of patients have other associated congenital anomalies; in particular, facial anomalies, such as cleft palate, are part of about 10% of the DBA clinical presentations.

Pierre Robin sequence (PRS) is a heterogeneous condition, defined by the presence of the triad of glossoptosis, micrognathia and cleft palate; it occurs in 1/8500 to 1/14,000 births.

Klippel Feil (KF) syndrome is a complex of both osseous and visceral anomalies, characterized mainly by congenital development defects of the cervical spine.

We describe the case of a 22-years-old woman affected by DBA, carrying a de novo deletion about 500 Kb-long at 12q13.2-q13.3 that included RPS26 and, at least, others 25 flanking genes. The patient showed craniofacial anomalies due to PRS and suffered for KF deformities (type II). Computed Tomography study of cranio-cervical junction (CCJ) drew out severe bone malformations and congenital anomalies as atlanto-occipital assimilation (AOA), arcuate foramen and occipito-condylar hyperplasia. Foramen magnum was severely reduced. Atlanto-axial instability (AAI) was linked to atlanto-occipital assimilation, congenital vertebral fusion and occipito-condyle bone hyperplasia. Basilar invagination and platybasia were ruled out on CT and Magnetic Resonance Imaging (MRI) studies. Furthermore, the temporal Bone CT study showed anomalies of external auditory canals, absent mastoid pneumatization, chronic middle ear otitis and abnormal course of the facial nerve bones canal.

The described phenotype might be related to the peculiar deletion affecting the patient, highlighting that genes involved in the in the breakdown of extracellular matrix (MMP19), in cell cycle regulation (CDK2), vesicular trafficking (RAB5B), in ribonucleoprotein complexes formation (ZC3H10) and muscles function (MYL6 and MYL6B) could be potentially related to bone-developmental disorders. Moreover, it points out that multiple associated ribosomal deficits might play a role in DBA-related phenotypes, considering the simultaneous deletion of three of them in the index case (RPS26, PA2G4 and RPL41), and it confirms the association among SLC39A5 functional disruption and severe myopia.

This report highlights the need for a careful genetic evaluation and a detailed phenotype-genotype correlation in each complex malformative syndrome.

Skeletal malformations of Meox1-deficient zebrafish resemble human Klippel-Feil syndrome

Klippel-Feil syndrome is a congenital vertebral anomaly, which is characterised by the fusion of at least two cervical vertebrae and a clinically broad set of symptoms, including congenital scoliosis and elevated scapula (Sprengel's deformity). Klippel-Feil syndrome is associated with mutations in MEOX1. The zebrafish mutant choker (cho) carries a mutation in its orthologue, meox1. Although zebrafish is being increasingly employed as fidelitous models of human spinal disease, the vertebral column of Meox1-deficient fish has not been assessed for defects. Here, we describe the skeletal defects of meox1^cho mutant zebrafish utilising alizarin red to stain bones and chemical maceration of soft tissue to detect fusions in an unbiased manner. Obtained data reveal that meox1^cho mutants feature aspects of a number of described symptoms of patients who suffer from Klippel-Feil syndrome and have mutations in MEOX1. These include vertebral fusion, congenital scoliosis and an asymmetry of the pectoral girdle, which resembles Sprengel's deformity. Thus, the meox1^cho mutant zebrafish may serve as a useful tool to study the pathogenesis of the symptoms associated with Klippel-Feil syndrome.

Neurocristopathies: New insights 150 years after the neural crest discovery

The neural crest (NC) is a transient, multipotent and migratory cell population that generates an astonishingly diverse array of cell types during vertebrate development. These cells, which originate from the ectoderm in a region lateral to the neural plate in the neural fold, give rise to neurons, glia, melanocytes, chondrocytes, smooth muscle cells, odontoblasts and neuroendocrine cells, among others. Neurocristopathies (NCP) are a class of pathologies occurring in vertebrates, especially in humans that result from the abnormal specification, migration, differentiation or death of neural crest cells during embryonic development. Various pigment, skin, thyroid and hearing disorders, craniofacial and heart abnormalities, malfunctions of the digestive tract and tumors can also be considered as neurocristopathies. In this review we revisit the current classification and propose a new way to classify NCP based on the embryonic origin of the affected tissues, on recent findings regarding the molecular mechanisms that drive NC formation, and on the increased complexity of current molecular embryology techniques.

Diagnostic strategy in segmentation defect of the vertebrae: a retrospective study of 73 patients

Background

Segmentation defects of the vertebrae (SDV) are non-specific features found in various syndromes. The molecular bases of SDV are not fully elucidated due to the wide range of phenotypes and classification issues. The genes involved are in the Notch signalling pathway, which is a key system in somitogenesis. Here we report on mutations identified in a diagnosis cohort of SDV. We focused on spondylocostal dysostosis (SCD) and the phenotype of these patients in order to establish a diagnostic strategy when confronted with SDV.

Patients and methods

We used DNA samples from a cohort of 73 patients and performed targeted sequencing of the five known SCD-causing genes (DLL3, MESP2, LFNG, HES7 and TBX6) in the first 48 patients and whole-exome sequencing (WES) in 28 relevant patients.

Results

Ten diagnoses, including four biallelic variants in TBX6, two biallelic variants in LFNG and DLL3, and one in MESP2 and HES7, were made with the gene panel, and two diagnoses, including biallelic variants in FLNB and one variant in MEOX1, were made by WES. The diagnostic yield of the gene panel was 10/73 (13.7%) in the global cohort but 8/10 (80%) in the subgroup meeting the SCD criteria; the diagnostic yield of WES was 2/28 (8%).

Conclusion

After negative array CGH, targeted sequencing of the five known SCD genes should only be performed in patients who meet the diagnostic criteria of SCD. The low proportion of candidate genes identified by WES in our cohort suggests the need to consider more complex genetic architectures in cases of SDV.

Novel cancer stem cell targets during epithelial to mesenchymal transition in PTEN-deficient trastuzumab-resistant breast cancer

Continued use of trastuzumab in PTEN-deficient HER2+ breast cancer induces the epithelial-to-mesenchymal transition (EMT), transforms HER2+ to triple negative breast cancer, and expands breast cancer stem cells (BCSCs). Using cancer cell lines with two distinct states, epithelial and mesenchymal, we identified novel targets during EMT in PTEN-deficient trastuzumab-resistant breast cancer. Differential gene expression and distinct responses to a small molecule in BT474 (HER2+ trastuzumab-sensitive) and the PTEN-deficient trastuzumab-resistant derivative (BT474-PTEN-LTT) provided the selection tools to identify targets during EMT. siRNA knockdown and small molecule inhibition confirmed MEOX1 as one of the critical molecular targets to regulate both BCSCs and mesenchymal-like cell proliferation. MEOX1 was associated with poor survival, lymph node metastasis, and stage of breast cancer patients. These findings suggest that MEOX1 is a clinically relevant novel target in BCSCs and mesenchymal-like cancer cells in PTEN-deficient trastuzumab resistant breast cancer and may serve as target for future drug development.

Klippel-Feil Syndrome with Sprengel Deformity and Extensive Upper Extremity Deformity: A Case Report and Literature Review

Introduction

Klippel-Feil syndrome (KFS) is a congenital anomaly resulting from fusion of cervical vertebral bodies secondary to the dysregulation of signaling pathways during somite development. It is commonly associated with scoliosis and Sprengel deformity. We present a case of KFS with commonly associated abnormalities as well as deformities that have not yet been reported in the literature.

Case Presentation

A 3-year-old girl presented for further evaluation of a left upper extremity deformity following a negative genetic workup. Upon physical exam and radiographic imaging, the patient was diagnosed with KFS and associated abnormalities including cervical scoliosis, Sprengel deformity, and congenital deformity of the left upper extremity. Deformities of the left upper extremity include radioulnar synostosis, a four-rayed hand, and absent thenar musculature. The Sprengel deformity was corrected surgically with a Woodward procedure.

Discussion

Congenital musculoskeletal deformities can be differentiated based upon spinal and limb embryology. The presence of extraspinal abnormalities not originating from somite differentiation may suggest a severe form of KFS. Important considerations in the workup of the KFS patient include looking for deformities of the shoulder girdle and upper extremities to identify abnormalities for intervention at a young age.

NAD Deficiency, Congenital Malformations, and Niacin Supplementation

BACKGROUND

Congenital malformations can be manifested as combinations of phenotypes that co-occur more often than expected by chance. In many such cases, it has proved difficult to identify a genetic cause. We sought the genetic cause of cardiac, vertebral, and renal defects, among others, in unrelated patients.

METHODS

We used genomic sequencing to identify potentially pathogenic gene variants in families in which a person had multiple congenital malformations. We tested the function of the variant by using assays of in vitro enzyme activity and by quantifying metabolites in patient plasma. We engineered mouse models with similar variants using the CRISPR (clustered regularly interspaced short palindromic repeats)-Cas9 system.

RESULTS

Variants were identified in two genes that encode enzymes of the kynurenine pathway, 3-hydroxyanthranilic acid 3,4-dioxygenase (HAAO) and kynureninase (KYNU). Three patients carried homozygous variants predicting loss-of-function changes in the HAAO or KYNU proteins (HAAO p.D162*, HAAO p.W186*, or KYNU p.V57Efs*21). Another patient carried heterozygous KYNU variants (p.Y156* and p.F349Kfs*4). The mutant enzymes had greatly reduced activity in vitro. Nicotinamide adenine dinucleotide (NAD) is synthesized de novo from tryptophan through the kynurenine pathway. The patients had reduced levels of circulating NAD. Defects similar to those in the patients developed in the embryos of Haao-null or Kynu-null mice owing to NAD deficiency. In null mice, the prevention of NAD deficiency during gestation averted defects.

CONCLUSIONS

Disruption of NAD synthesis caused a deficiency of NAD and congenital malformations in humans and mice. Niacin supplementation during gestation prevented the malformations in mice. (Funded by the National Health and Medical Research Council of Australia and others.).

Filamin B Loss-of-Function Mutation in Dimerization Domain Causes Autosomal-Recessive Spondylocarpotarsal Synostosis Syndrome with Rib Anomalies

Spondylocarpotarsal synostosis syndrome (SCT) is a distinct group of disorders characterized by short stature, disrupted vertebral segmentation with vertebral fusion, scoliosis, lordosis, carpal/tarsal synostosis, and lack of rib anomalies. Mutations in filamin B (FLNB) and MYH3 have been reported for autosomal-recessive and autosomal-dominant SCT, respectively. We present a family with two patients suffering from autosomal-recessive SCT with rib anomalies, including malalignment, crowding, and uneven size and shape of ribs. Whole-exome sequencing revealed a novel p.S2542Lfs^* 82 (c.7621dup) frameshift mutation in FLNB. This frameshift mutation lies in the C-terminal-most domain involved in FLNB dimerization and resulted in a 20-residue elongation, with complete familial segregation and absence in 376 normal controls. The mutant p.S2542Lfs^* 82 FLNB demonstrated a complete loss of ability to form a functional dimer in transiently transfected HEK293T cells. The p.S2542Lfs^* 82 mutation also led to significantly reduced protein levels and accumulation of the mutant protein in the Golgi apparatus. This is the first identified mutation in the dimerization domain of FLNB. This loss-of-function frameshift mutation in FLNB causes autosomal-recessive SCT with rarely reported rib anomalies. This report demonstrates the involvement of rib anomaly in SCT and its causative mutation in the dimerization domain of FLNB.

The corticospinal tract: Evolution, development, and human disorders

The corticospinal tract (CST) plays a major role in cortical control of spinal cord activity. In particular, it is the principal motor pathway for voluntary movements. Here, we discuss: (i) the anatomic evolution and development of the CST across mammalian species, focusing on its role in motor functions; (ii) the molecular mechanisms regulating corticospinal tract formation and guidance during mouse development; and (iii) human disorders associated with abnormal CST development. A comparison of CST anatomy and development across mammalian species first highlights important similarities. In particular, most CST axons cross the anatomical midline at the junction between the brainstem and spinal cord, forming the pyramidal decussation. Reorganization of the pattern of CST projections to the spinal cord during evolution led to improved motor skills. Studies of the molecular mechanisms involved in CST formation and guidance in mice have identified several factors that act synergistically to ensure proper formation of the CST at each step of development. Human CST developmental disorders can result in a reduction of the CST, or in guidance defects associated with abnormal CST anatomy. These latter disorders result in altered midline crossing at the pyramidal decussation or in the spinal cord, but spare the rest of the CST. Careful appraisal of clinical manifestations associated with CST malformations highlights the critical role of the CST in the lateralization of motor control. © 2016 Wiley Periodicals, Inc. Develop Neurobiol 77: 810-829, 2017.

The intriguing history of vertebral fusion anomalies: the Klippel-Feil syndrome

INTRODUCTION

Our knowledge and understanding of vertebral fusion, defined and eponymously known as Klippel-Feil syndrome in the early 1900s, have a long history. This uncommon finding has been identified as early as 500 B.C. in an Egyptian mummy. Many more examples of spinal vertebra fusion have been described by Greek historians and recovered by archeologists demonstrating this entity's rich history.

CONCLUSIONS

Klippel-Feil syndrome is a rare skeletal anomaly characterized by abnormal fusion of two or more vertebrae. With the advent of newer molecular technology and genetic discoveries, we now have a better understanding of the etiology and possible pathogenesis of this disease.

Rare variants in the notch signaling pathway describe a novel type of autosomal recessive Klippel-Feil syndrome

Klippel-Feil syndrome is a rare disorder represented by a subgroup of segmentation defects of the vertebrae and characterized by fusion of the cervical vertebrae, low posterior hairline, and short neck with limited motion. Both autosomal dominant and recessive inheritance patterns were reported in families with Klippel-Feil. Mutated genes for both dominant (GDF6 and GDF3) and recessive (MEOX1) forms of Klippel-Feil syndrome have been shown to be involved in somite development via transcription regulation and signaling pathways. Heterotaxy arises from defects in proteins that function in the development of left-right asymmetry of the developing embryo. We describe a consanguineous family with a male proband who presents with classical Klippel-Feil syndrome together with heterotaxy (situs inversus totalis). The present patient also had Sprengel's deformity, deformity of the sternum, and a solitary kidney. Using exome sequencing, we identified a homozygous frameshift mutation (c.299delT; p.L100fs) in RIPPLY2, a gene shown to play a crucial role in somitogenesis and participate in the Notch signaling pathway via negatively regulating Tbx6. Our data confirm RIPPLY2 as a novel gene for autosomal recessive Klippel-Feil syndrome, and in addition-from a mechanistic standpoint-suggest the possibility that mutations in RIPPLY2 could also lead to heterotaxy. © 2015 Wiley Periodicals, Inc.

Advances in Skeletal Dysplasia Genetics

Skeletal dysplasias result from disruptions in normal skeletal growth and development and are a major contributor to severe short stature. They occur in approximately 1/5,000 births, and some are lethal. Since the most recent publication of the Nosology and Classification of Genetic Skeletal Disorders, genetic causes of 56 skeletal disorders have been uncovered. This remarkable rate of discovery is largely due to the expanded use of high-throughput genomic technologies. In this review, we discuss these recent discoveries and our understanding of the molecular mechanisms behind these skeletal dysplasia phenotypes. We also cover potential therapies, unusual genetic mechanisms, and novel skeletal syndromes both with and without known genetic causes. The acceleration of skeletal dysplasia genetics is truly spectacular, and these advances hold great promise for diagnostics, risk prediction, and therapeutic design.

A novel syndrome of Klippel-Feil anomaly, myopathy, and characteristic facies is linked to a null mutation in MYO18B

BACKGROUND

Klippel-Feil anomaly (KFA) can be seen in a number of syndromes. We describe an apparently novel syndromic association with KFA.

METHODS

Clinical phenotyping of two consanguineous families followed by combined autozygome/exome analysis.

RESULTS

Two patients from two apparently unrelated families shared a strikingly similar phenotype characterised by KFA, myopathy, mild short stature, microcephaly, and distinctive facies. They shared a single founder autozygous interval in which whole exome sequencing revealed a truncating mutation in MYO18B. There was virtually complete loss of the transcript in peripheral blood, indicative of nonsense-mediated decay. Electron microscopy of muscle confirms abnormal myosin filaments with accompanying myopathic changes.

CONCLUSIONS

Deficiency of MYO18B is linked to a novel developmental disorder which combines KFA with myopathy. This suggests a widespread developmental role for this gene in humans, as observed for its murine ortholog.

Klippel-Feil syndrome and levo-looped transposition of the great arteries

Klippel-Feil syndrome is a skeletal disorder characterised by low hairline and a short neck due to abnormal fusion of two or more cervical vertebrae. Although congenital heart and lung defects are infrequent, some abnormalities such as cor triatriatum, coarctation of the aorta, total anomalous pulmonary venous connection, or lung agenesis have been reported. The challenge of recognising Klippel-Feil syndrome lies in the fact that there is an association of this syndrome with other significant conditions such as skeletal, genitourinary, neurological, ear, and some cardiac defects. We report a Klippel-Feil syndrome type III 14-year-old patient with a levo-looped transposition of the great arteries. In addition, the patient had agenesis of the left upper-lung lobe.