Characterization of a New Variant in ARHGAP31 Probably Involved in Adams-Oliver Syndrome in a Family with a Variable Phenotypic Spectrum.

Adams-Oliver syndrome is a rare inherited condition characterized by scalp defects and limb abnormalities. It is caused by variants in different genes such as ARHGAP31. Here, we used an interdisciplinary approach to study a family with lower limb anomalies. We identified a novel variant in the ARHGAP31 gene that is predicted to result in a truncated protein with a constitutively activated catalytic site due to the loss of 688 amino acids involved in the C-terminal domain, essential for protein auto-inhibition. Pathogenic variants in ARHGAP31 exon 12, leading to a premature protein termination, are associated with Adams-Oliver syndrome. Bioinformatic analysis was useful to elucidate the impact of the identified genetic variant on protein structure. To better understand the impact of the identified variant, 3D protein models were predicted for the ARHGAP31 wild type, the newly discovered variant, and other pathogenetic alterations already reported. Our study identified a novel variant probably involved in Adams-Oliver syndrome and increased the evidence on the phenotypic variability in patients affected by this syndrome, underlining the importance of translational research, including experimental and bioinformatics analyses. This strategy represents a successful model to investigate molecular mechanisms involved in syndrome occurrence.

Prenatal diagnosis of ROR-2 related Robinow syndrome presenting with fetal ultrasound findings of mesomelia, vertebral, digital and genital abnormalities.

Autosomal recessive ROR2-Robinow syndrome is caused by pathogenic variants in the ROR2 gene. Fetal ultrasound done on our patient at 24 + 3/7 weeks gestation showed macrocephaly, brachycephaly, flat face, prominent forehead, mild frontal bossing, lower thoracic hemivertebrae, digital abnormalities and micropenis. Fetal trio whole exome sequencing done on amniocytes showed two pathogenic compound heterozygous variants in the ROR2 gene, c.1324 C > T; p.(Arg442*) maternally inherited and c.1366dup; p.(Leu456Profs*3) apparently de novo. c.1324 C > T; p.(Arg442*) is a nonsense variant resulting in protein truncation reported to be associated with RRS3. c.1366dup; p.(Leu456Profs*3) is a frameshift variant predicted to result in protein truncation reported to segregate with the disease in multiple affected individuals from a single large family with distal symphalangism of the fourth finger. Fetal autopsy following pregnancy termination showed a large head with low-set ears, facial abnormalities, mesomelic bone shortening, hemivertebra, fused S3 and S4 vertebral bodies, several fused rib heads and short penis with buried shaft.

Heterozygous MAP3K20 variants cause ectodermal dysplasia, craniosynostosis, sensorineural hearing loss, and limb anomalies.

Biallelic pathogenic variants in MAP3K20, which encodes a mitogen-activated protein kinase, are a rare cause of split-hand foot malformation (SHFM), hearing loss, and nail abnormalities or congenital myopathy. However, heterozygous variants in this gene have not been definitively associated with a phenotype. Here, we describe the phenotypic spectrum associated with heterozygous de novo variants in the linker region between the kinase domain and leucine zipper domain of MAP3K20. We report five individuals with diverse clinical features, including craniosynostosis, limb anomalies, sensorineural hearing loss, and ectodermal dysplasia-like phenotypes who have heterozygous de novo variants in this specific region of the gene. These individuals exhibit both shared and unique clinical manifestations, highlighting the complexity and variability of the disorder. We propose that the involvement of MAP3K20 in endothelial-mesenchymal transition provides a plausible etiology of these features. Together, these findings characterize a disorder that both expands the phenotypic spectrum associated with MAP3K20 and highlights the need for further studies on its role in early human development.

Monodactyly in a patient with CHARGE syndrome: An additional case report.

CHARGE syndrome is a rare autosomal dominant syndrome characterized by multiple congenital anomalies including coloboma, heart defects, ear anomalies, and developmental delay, caused by pathogenic variants in the CHD7 gene. The discovery of the molecular basis of this syndrome increased the number of cases reported and expanded the phenotype and clinical variability. Limb anomalies are occasional clinical findings in this syndrome, present in about 30% of reported cases. The occurrence of limb anomalies in this syndrome suggests that it should be considered as part of the phenotypic spectrum. Here, we describe an individual with CHARGE syndrome presenting unilateral monodactyly.

Split-hand/foot malformation 3 resulting from microduplications in 10q24 region in five patients from India.

Split-hand/foot malformation (SHFM) is a genetically heterogeneous congenital limb reduction defect characterized by the deficiencies of central rays of the autopod. Tandem duplications at 10q24 locus account for approximately 20% of all SHFM cases. Here, we report five affected individuals from four unrelated Indian families with SHFM3 caused by microduplication of 10q24 locus showing varied clinical presentations. This report substantiates and extends the current understanding of this rare, multifaceted, and complex condition.

A novel genotype-phenotype between persistent-cloaca-related VACTERL and mutations of 8p23 and 12q23.1.

The mechanism underlying anorectal malformations (ARMs)-related VACTERL (vertebral defects, anal atresia, cardiac defects, tracheo-esophageal fistula, and renal and limb abnormalities) remains unclear. Copy number variation (CNV) contributed to VACTERL pathogenicity. Here, we report a novel CNV in 8p23 and 12q23.1 identified in a case of ARMs-related VACTERL association. This 12-year-old girl presented a cloaca (urethra, vagina, and rectum opening together and sharing a single tube length), an isolated kidney, and a perpetuation of the left superior vena cava at birth. Her intelligence, growth, and development were slightly lower than those of normal children of the same age. Array comparative genomic hybridization revealed a 9.6-Mb deletion in 8p23.1-23.3 and a 0.52-Mb duplication in 12q23.1 in her genome. Furthermore, we reviewed the cases involving CNVs in patients with VACTERL, 8p23 deletion, and 12q23.1 duplication, and our case was the first displaying ARMs-related VACTERL association with CNV in 8p23 and 12q23.1. These findings enriched our understanding between VACTERL association and the mutations of 8p23 deletion and 12q23.1 duplication. IMPACT: This is a novel case of a Chinese girl with anorectal malformations (ARMs)-related VACTERL with an 8p23.1-23.3 deletion and 12q23.1 duplication. Cloaca malformation is presented with novel copy number variation in 8p23.1-23.3 deletion and 12q23.1 duplication.

Split Hand-Foot and Deafness in a Patient with 7q21.13-q21.3 Deletion Not Including the DLX5/6 Genes.

Split Hand-Foot Malformation (SHFM) is a congenital limb defect characterized by a median cleft of the hands and/or feet due to the absence/hypoplasia of the central rays. It may occur as part of a syndromic condition or as an isolated malformation. The most common of the six genetic loci identified for this condition is correlated to SHFM1 and maps in the 7q21q22 region. SHFM1 is characterized by autosomal dominant transmission, incomplete penetrance and variable expressivity. Associated features often include hearing loss, intellectual disability/developmental delay and craniofacial abnormalities. Disruption of the DLX5/DLX6 genes, mapping within the SHFM1 locus, is now known to be responsible for the phenotype. Through SNP array, we analyzed a patient affected by SHFM1 associated with deafness and an abnormality of the inner ear (incomplete partition type I); we identified a deletion in 7q21, not involving the DLX5/6 genes, but including exons 15 and 17 of DYNC1I1, known to act as exonic enhancers (eExons) of the DLX5/6 genes. We further demonstrated the role of DYNC1I1 eExons in regulating DLX5/6 expression by means of showing a reduced expression of the DLX5/6 genes through RT-PCR in a patient-derived lymphoblastoid cell line. Furthermore, our data and a review of published cases do not support the hypothesis that DLX5/6 are imprinted in humans. This work is an example of how the disruption of regulatory elements can be responsible for congenital malformations.

A complex structural variant near SOX3 causes X-linked split-hand/foot malformation.

Split-hand/foot malformation (SHFM) is a congenital limb defect most typically presenting with median clefts in hands and/or feet, that can occur in a syndromic context as well as in isolated form. SHFM is caused by failure to maintain normal apical ectodermal ridge function during limb development. Although several genes and contiguous gene syndromes are implicated in the monogenic etiology of isolated SHFM, the disorder remains genetically unexplained for many families and associated genetic loci. We describe a family with isolated X-linked SHFM, for which the causative variant could be detected after a diagnostic journey of 20 years. We combined well-established approaches including microarray-based copy number variant analysis and fluorescence in situ hybridization coupled with optical genome mapping and whole genome sequencing. This strategy identified a complex structural variant (SV) comprising a 165-kb gain of 15q26.3 material ([GRCh37/hg19] chr15:99795320-99960362dup) inserted in inverted position at the site of a 38-kb deletion on Xq27.1 ([GRCh37/hg19] chrX:139481061-139518989del). In silico analysis suggested that the SV disrupts the regulatory framework on the X chromosome and may lead to SOX3 misexpression. We hypothesize that SOX3 dysregulation in the developing limb disturbed the fine balance between morphogens required for maintaining AER function, resulting in SHFM in this family.

PRDM1 DNA-binding zinc finger domain is required for normal limb development and is disrupted in split hand/foot malformation.

Split hand/foot malformation (SHFM) is a rare limb abnormality with clefting of the fingers and/or toes. For many individuals, the genetic etiology is unknown. Through whole-exome and targeted sequencing, we detected three novel variants in a gene encoding a transcription factor, PRDM1, that arose de novo in families with SHFM or segregated with the phenotype. PRDM1 is required for limb development; however, its role is not well understood and it is unclear how the PRDM1 variants affect protein function. Using transient and stable overexpression rescue experiments in zebrafish, we show that the variants disrupt the proline/serine-rich and DNA-binding zinc finger domains, resulting in a dominant-negative effect. Through gene expression assays, RNA sequencing, and CUT&RUN in isolated pectoral fin cells, we demonstrate that Prdm1a directly binds to and regulates genes required for fin induction, outgrowth and anterior/posterior patterning, such as fgfr1a, dlx5a, dlx6a and smo. Taken together, these results improve our understanding of the role of PRDM1 in the limb gene regulatory network and identified novel PRDM1 variants that link to SHFM in humans.

Al-Gazali Skeletal Dysplasia Constitutes the Lethal End of ADAMTSL2-Related Disorders.

Lethal short-limb skeletal dysplasia Al-Gazali type (OMIM %601356), also called dysplastic cortical hyperostosis, Al-Gazali type, is an ultra-rare disorder previously reported in only three unrelated individuals. The genetic etiology for Al-Gazali skeletal dysplasia has up until now been unknown. Through international collaborative efforts involving seven clinical centers worldwide, a cohort of nine patients with clinical and radiographic features consistent with short-limb skeletal dysplasia Al-Gazali type was collected. The affected individuals presented with moderate intrauterine growth restriction, relative macrocephaly, hypertrichosis, large anterior fontanelle, short neck, short and stiff limbs with small hands and feet, severe brachydactyly, and generalized bone sclerosis with mild platyspondyly. Biallelic disease-causing variants in ADAMTSL2 were detected using massively parallel sequencing (MPS) and Sanger sequencing techniques. Six individuals were compound heterozygous and one individual was homozygous for pathogenic variants in ADAMTSL2. In one of the families, pathogenic variants were detected in parental samples only. Overall, this study sheds light on the genetic cause of Al-Gazali skeletal dysplasia and identifies it as a semi-lethal part of the spectrum of ADAMTSL2-related disorders. Furthermore, we highlight the importance of meticulous analysis of the pseudogene region of ADAMTSL2 where disease-causing variants might be located. © 2023 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

Feingold syndrome type 1: a rare cause of fetal microcephaly (prenatal diagnosis).

We report a case of fetal microcephaly found during the second trimester ultrasound and confirmed by further ultrasound scans and fetal MRI. The array comparative genomic hybridisation analysis of the fetus and the male parent showed a 1.5 Mb deletion overlapping the Feingold syndrome region, an autosomal dominant syndrome that can cause microcephaly, facial/hand abnormalities, mild neurodevelopmental delay and others. This case illustrates the need for a detailed investigation by a multidisciplinary team to provide prenatal counselling regarding a postnatal outcome to the parents and orient their decision towards the continuation or termination of pregnancy.

NOTCH1 loss of the TAD and PEST domain: An antimorph?

The Notch proteins play key roles in cell fate determination during development. Germline pathogenic variants in NOTCH1 predispose to a spectrum of cardiovascular malformations including Adams-Oliver syndrome and a wide variety of isolated complex and simple congenital heart defects. The intracellular C-terminus of the single-pass transmembrane receptor encoded by NOTCH1 contains a transcriptional activating domain (TAD) required for target gene activation and a PEST domain (a sequence rich in proline, glutamic acid, serine, and threonine), regulating protein stability and turnover. We present a patient with a novel variant encoding a truncated NOTCH1 protein without the TAD and PEST domain (NM_017617.4: c.[6626_6629del];[=], p.(Tyr2209CysfsTer38)) and extensive cardiovascular abnormalities consistent with a NOTCH1-mediated mechanism. This variant fails to promote transcription of target genes as assessed by luciferase reporter assay. Given the roles of the TAD and PEST domains in NOTCH1 function and regulation, we hypothesize that loss of both the TAD and the PEST domain results in a stable, loss-of-function protein that acts as an antimorph through competition with wild-type NOTCH1.

Combinatorial effects on gene expression at the Lbx1/Fgf8 locus resolve split-hand/foot malformation type 3.

Split-Hand/Foot Malformation type 3 (SHFM3) is a congenital limb malformation associated with tandem duplications at the LBX1/FGF8 locus. Yet, the disease patho-mechanism remains unsolved. Here we investigate the functional consequences of SHFM3-associated rearrangements on chromatin conformation and gene expression in vivo in transgenic mice. We show that the Lbx1/Fgf8 locus consists of two separate, but interacting, regulatory domains. Re-engineering of a SHFM3-associated duplication and a newly reported inversion in mice results in restructuring of the chromatin architecture. This leads to ectopic activation of the Lbx1 and Btrc genes in the apical ectodermal ridge (AER) in an Fgf8-like pattern induced by AER-specific enhancers of Fgf8. We provide evidence that the SHFM3 phenotype is the result of a combinatorial effect on gene misexpression in the developing limb. Our results reveal insights into the molecular mechanism underlying SHFM3 and provide conceptual framework for how genomic rearrangements can cause gene misexpression and disease.

Successful therapeutic intervention in new mouse models of frizzled 2-associated congenital malformations.

Frizzled 2 (FZD2) is a transmembrane Wnt receptor. We previously identified a pathogenic human FZD2 variant in individuals with FZD2-associated autosomal dominant Robinow syndrome. The variant encoded a protein with a premature stop and loss of 17 amino acids, including a region of the consensus dishevelled-binding sequence. To model this variant, we used zygote microinjection and i-GONAD-based CRISPR/Cas9-mediated genome editing to generate a mouse allelic series. Embryos mosaic for humanized Fzd2W553* knock-in exhibited cleft palate and shortened limbs, consistent with patient phenotypes. We also generated two germline mouse alleles with small deletions: Fzd2D3 and Fzd2D4. Homozygotes for each allele exhibit a highly penetrant cleft palate phenotype, shortened limbs compared with wild type and perinatal lethality. Fzd2D4 craniofacial tissues indicated decreased canonical Wnt signaling. In utero treatment with IIIC3a (a DKK inhibitor) normalized the limb lengths in Fzd2D4 homozygotes. The in vivo replication represents an approach for further investigating the mechanism of FZD2 phenotypes and demonstrates the utility of CRISPR knock-in mice as a tool for investigating the pathogenicity of human genetic variants. We also present evidence for a potential therapeutic intervention.

Spectrum of fetal limb anomalies.

PURPOSE: Antenatal detection of limb anomalies is not uncommon, and pregnancies are usually terminated in view of the expected physical handicap. The aim of this retrospective observational study is to delineate the spectrum of fetal limb anomalies and provide evidence in support of complete postnatal evaluation in establishing recurrence risk. METHODS: We present 54 cases of limb malformations detected antenatally and discuss the spectrum of abnormalities, the utility of fetal autopsy, and genetic testing to establish recurrence risk in subsequent pregnancies. RESULTS: 16/54 cases were isolated radial ray anomalies. There were five cases of amniotic band syndrome, five limb body wall complex cases, three VACTERL (vertebral defects, anal atresia, cardiac defects, tracheo-esophageal fistula, renal anomalies, and limb abnormalities) associations, one case of sirenomelia, two cases of limb pelvis hypoplasia, and one case of OEIS (Omphalocele Exstrophy Imperforate anus and spinal defects). Four fetuses with non-isolated radial ray anomaly had trisomy 18. One case with bilateral radial ray defect had a mutation in the FANC-E gene confirming fanconi anemia. Twelve cases were unclassified. CONCLUSION: Autopsy is the most important investigation in fetuses with limb anomalies. We suggest chromosomal microarray (CMA) as a first-tier test after autopsy. However, in cases of bilaterally symmetrical limb anomalies, in case of previous similarly affected child, or history of consanguinity, whole exome sequencing (WES) can be offered as the primary investigation, followed by CMA if WES is normal.

BHLHA9 homozygous duplication in a consanguineous family: A challenge for genetic counseling.

Split-hand/foot malformation (SHFM) with long-bone deficiency (SHFLD) is a rare condition characterized by SHFM associated with long-bone malformation usually involving the tibia. It includes three different types; SHFLD1 (MIM % 119,100), SHFLD2 (MIM % 610,685) and SHFLD3 (MIM # 612576). The latter was shown to be the most commonly reported with a duplication in the 17p13.1p13.3 locus that was narrowed down to the BHLHA9 gene. Here, we report a consanguineous Lebanese family with three members presenting with limb abnormalities including tibial hemimelia. One of these patients presented with additional bowing fibula and another with bilateral split hand. CGH array analysis followed by RQ-PCR allowed us to detect the first homozygous duplication on the short arm of chromosome 17p13.3 including the BHLHA9 gene and involved in SHFLD3. Interestingly, one patient with the homozygous duplicated region, carrying thus four BHLHA9 copies presented with long bone deficiency but no SHFM. The incomplete penetrance and the variable expressivity of the disease in this family as well as the presence of the BHLHA9 homozygous duplication rendered genetic counseling extremely challenging and preimplantation genetic diagnosis almost impossible.

Retrospective evaluation of clinical and molecular data of 148 cases of esophageal atresia.

Developmental abnormalities provide a unique opportunity to seek for the molecular mechanisms underlying human organogenesis. Esophageal development remains incompletely understood and elucidating causes for esophageal atresia (EA) in humans would contribute to achieve a better comprehension. Prenatal detection, syndromic classification, molecular diagnosis, and prognostic factors in EA are challenging. Some syndromes have been described to frequently include EA, such as CHARGE, EFTUD2-mandibulofacial dysostosis, Feingold syndrome, trisomy 18, and Fanconi anemia. However, no molecular diagnosis is made in most cases, including frequent associations, such as Vertebral-Anal-Cardiac-Tracheo-Esophageal-Renal-Limb defects (VACTERL). This study evaluates the clinical and genetic test results of 139 neonates and 9 fetuses followed-up at the Necker-Enfants Malades Hospital over a 10-years period. Overall, 52 cases were isolated EA (35%), and 96 were associated with other anomalies (65%). The latter group is divided into three subgroups: EA with a known genomic cause (9/148, 6%); EA with Vertebral-Anal-Cardiac-Tracheo-Esophageal-Renal-Limb defects (VACTERL) or VACTERL/Oculo-Auriculo-Vertebral Dysplasia (VACTERL/OAV) (22/148, 14%); EA with associated malformations including congenital heart defects, duodenal atresia, and diaphragmatic hernia without known associations or syndromes yet described (65/148, 44%). Altogether, the molecular diagnostic rate remains very low and may underlie frequent non-Mendelian genetic models.

A novel variant in AFF3 underlying isolated syndactyly.

Isolated syndactyly is a common limb malformation with limited known genetic etiology. We used exome sequencing to discover a novel heterozygous missense variant c.2915G > C: p.Arg972Pro in AFF3 on chromosome 2q11.2 in a family with isolated syndactyly in hands and feet. AFF3 belongs to a family of nuclear transcription activating factors and is involved in limb dorsoventral patterning. The variant Arg972Pro is located near the C terminus, a region that is yet to be associated with human disorders. Functional studies did not show a difference in the stability or subcellular localization of the mutant and wild type proteins. Instead, overexpression in zebrafish embryos suggests that Arg972Pro is a loss-of-function allele. These results suggest that variants in the C terminus of AFF3 may cause a phenotype distinct from previously characterized AFF3 variants.

ERI1: A case report of an autosomal recessive syndrome associated with developmental delay and distal limb abnormalities.

ERI1 is an evolutionary conserved 3'-5' exonuclease with an important function in multiple RNA processing pathways. Although the molecular mechanisms in which ERI1 is involved have been studied extensively in model organisms, the pathology associated with ERI1 variants in humans has remained elusive because no case has been reported so far. Here, we present a case of a female patient with a homozygous nonsense variant in ERI1 gene. The patient exhibits mild intellectual disability, eyelid ptosis, and anomalies in her hands and feet (brachydactyly, clinodactyly, dysplastic/short nail of halluces, brachytelephalangy, short metacarpals, and toe syndactyly). This case report is the first of its kind and is invaluable for understanding ERI1 pathology in humans.