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.

Investigating the role connective tissue fibroblasts play in the altered muscle anatomy associated with the limb abnormality, Radial Dysplasia

Radial dysplasia (RD) is a congenital upper limb birth defect that presents with changes to the upper limb anatomy, including a shortened or absent radius, bowed ulna, thumb malformations, a radially deviated hand and a range of muscle and tendon malformations, including absent or abnormally shaped muscle bundles. Current treatments to address wrist instability caused by a shortened or absent radius frequently require an initial soft tissue distraction intervention followed by a wrist stabilisation procedure. Following these surgical interventions, however, recurrence of the wrist deviation remains a common, long-term problem following treatment. The impact of the abnormal soft connective tissue (muscle and tendon) anatomy on the clinical presentation of RD and the complications following surgery are not understood. To address this, we have examined the muscle, fascia and the fascial irregular connective tissue (ICT) fibroblasts found within soft connective tissues, from RD patients. We show that ICT fibroblasts isolated from RD patients are functionally abnormal when compared to the same cells isolated from control patients and secrete a relatively disordered extracellular matrix (ECM). Furthermore, we show that ICT fibroblast dysfunction is a unifying feature found in RD patients, even when the RD clinical presentation is caused by distinct genetic syndromes.

Conformational Defects in the Limbs of Menorca Purebred Horses and Their Relationship to Functionality

Limb-conformation defects significantly influence equine performance and welfare, necessitating thorough investigation for effective management. This study examines the prevalence and genetic parameters of 14 limb-conformation defects in Menorca Purebred horses using data from 1120 records (509 animals with an average age of 101.87 ± 1.74 months) collected between 2015 and 2023. Defects were evaluated using a three-class scale by three appraisers, and a Bayesian approach via Gibbs sampling was employed to estimate genetic parameters including gender, birth period, stud selection criteria, evaluation age and appraiser as fixed effects. Splay-footed forelimb and closed hocks were the most prevalent defects (67.20% and 62.53%, respectively). Horses with any of the defects analyzed have been observed to obtain significantly lower scores for both walk and trot. Heritability estimates range from 0.12 (s.d.: 0.025) for closed hock to 0.30 (s.d.: 0.054) for base narrow, confirming the genetic influences on the expression of limb conformation defects. The divergent defect in hind limbs showed the highest genetic correlations with forelimb defects (camped under, -0.69; s.d: 0.32 and camped out, 0.70; s.d: 0.27). The significant genetic correlations between defects highlight the complexity of the relationships, which requires careful consideration.

POLR1A variants underlie phenotypic heterogeneity in craniofacial, neural, and cardiac anomalies

Heterozygous pathogenic variants in POLR1A, which encodes the largest subunit of RNA Polymerase I, were previously identified as the cause of acrofacial dysostosis, Cincinnati-type. The predominant phenotypes observed in the cohort of 3 individuals were craniofacial anomalies reminiscent of Treacher Collins syndrome. We subsequently identified 17 additional individuals with 12 unique heterozygous variants in POLR1A and observed numerous additional phenotypes including neurodevelopmental abnormalities and structural cardiac defects, in combination with highly prevalent craniofacial anomalies and variable limb defects. To understand the pathogenesis of this pleiotropy, we modeled an allelic series of POLR1A variants in vitro and in vivo. In vitro assessments demonstrate variable effects of individual pathogenic variants on ribosomal RNA synthesis and nucleolar morphology, which supports the possibility of variant-specific phenotypic effects in affected individuals. To further explore variant-specific effects in vivo, we used CRISPR-Cas9 gene editing to recapitulate two human variants in mice. Additionally, spatiotemporal requirements for Polr1a in developmental lineages contributing to congenital anomalies in affected individuals were examined via conditional mutagenesis in neural crest cells (face and heart), the second heart field (cardiac outflow tract and right ventricle), and forebrain precursors in mice. Consistent with its ubiquitous role in the essential function of ribosome biogenesis, we observed that loss of Polr1a in any of these lineages causes cell-autonomous apoptosis resulting in embryonic malformations. Altogether, our work greatly expands the phenotype of human POLR1A-related disorders and demonstrates variant-specific effects that provide insights into the underlying pathogenesis of ribosomopathies.

Burden of congenital and hereditary anomalies in the war-affected territory at Pakistan-Afghanistan border

Background

Pashtun populations of Pakistan are the victim of long-lasting military combats, rendering 1.9 million inhabitants internally displaced. Studies highlighting congenital and hereditary anomalies in these populations are deficient.

Objectives

To elucidate the spectrum anomalies in the north-western war-affected territories of Pakistan.

Methods

A cross-sectional study was carried out from 2017 to 2019 and individuals or families with anomalies were ascertained through convenience and cluster random sampling. Phenotypic and pedigree data and information on bio-demographic variables were collected. Descriptive statistics were applied.

Results

A total of 361 independent individuals or families with anomalies were recruited. The anomalies were grouped into 8 major and 72 minor entities. Among major categories, neurological disorders had the highest representation (n = 100; proportion: 0.277; 95% CI: 0.231-0.323), followed by sensorineural defects (n = 70; prop.: 0.194), limb defects (n = 60; prop.: 0.166), visual impairments (n = 55; prop.: 0.152), and musculoskeletal defects (n = 37; prop.: 0.102). Among the neurological disorders, intellectual disability had the highest occurrence (58%), whereas talipes and limb amputations were the most prominent in limb defects (22% and 20%, respectively). The anomalies had sporadic and isolated presentations most often (76% each), while parental consanguinity was observed in 34% of index cases.

Conclusions

The high incidence of neurological, sensorineural, and limb defects, the preponderance of sporadic cases, and low level of parental consanguinity may indicate a potentially high contribution of nongenetic factors in the etiology of anomalies. The majority of anomalies are the cause of severe disability.

Rare Presentation of Limb-Body Wall Complex in a Neonate: Case Report and Review of Literature

The limb-body wall complex (LBWC) aka body stalk syndrome is an uncommon congenital disorder characterized by severe malformations of limb, thorax, and abdomen, characterized by the presence of thoracoschisis, abdominoschisis, limb defects, and exencephaly. This condition is extremely rare with an incidence of 1 per 14,000 and 1 per 31,000 pregnancies in large epidemiologic studies. Majority of these malformed fetuses end up with spontaneous abortions. We present this rare case with occurrence in a preterm infant of 35 weeks' gestation. Our report highlights majority of the clinical presentations as reported in previous literature, but the significant pathological findings of absent genitalia and malformed genitourinary as well as anorectal malformations make this case presentation an even more rare occurrence. Infant karyotyping was normal male and there is no specific underlying genetic correlation in this condition which has a fatal prognosis.

Congenital limb defects in a married female population of the Rahim Yar Khan District in Pakistan

Background

Congenital limb defects (CLD) have a range of phenotypes and can be a substantial cause of disability. The prevalence of CLD in the adult population of Pakistan is not well described.

Objectives

To investigate the prevalence of CLD and their associated factors in a married female population of the Rahim Yar Khan (RYK) District in Pakistan.

Methods

A cross-sectional population-based study was conducted in 4 tehsils of RYK District, and married women and girls from 22 different localities were enrolled by convenience sampling in public places and through door-to-door visits. Data regarding limb phenotype and demographic variables were obtained from participants.

Results

We enrolled 2,204 married women and girls. We found 11 participants with CLD suggesting a prevalence of 4.99/1,000 (proportion: 0.005; 95% confidence interval [CI] <0.001-0.01). Polydactyly was the most frequent (n = 5; prevalence: 2.27/1,000), followed by others in the following sequence: brachydactyly (n = 4; prevalence: 1.81/1,000), camptodactyly (n = 1; prevalence: 0.45/1,000), and oligodactyly (n = 1; prevalence: 0.45/1,000). The odds of occurrence of CLD were higher in individuals originating from Khanpur tehsil (odds ratio [OR] 2.05; 95% CI 0.37-11.27), speaking languages other than Punjabi and Saraiki (OR 2.35; 95% CI 0.24-22.80), belonging to Araien caste (OR 2.35; 95% CI: 0.24-22.80), of a nuclear family (OR 3.35; 95% CI 0.79-16.97), or having parental consanguinity (OR 1.87; 95% CI 0.49-7.06).

Conclusion

Preliminary estimate of CLD prevalence in the married female sample population in RYK appears high compared with estimates from birth defects registries in other countries.

Mutations in gene regulatory elements linked to human limb malformations

Most of the human genome has a regulatory function in gene expression. The technological progress made in recent years permitted the revision of old and discovery of new mutations outside of the protein-coding regions that do affect human limb morphology. Steadily increasing discovery rate of such mutations suggests that until now the largely neglected part of the genome rises to its well-deserved prominence. In this review, we describe the recent technological advances permitting this unprecedented advance in identifying non-coding mutations. We especially focus on the mutations in cis-regulatory elements such as enhancers, and trans-regulatory elements such as miRNA and long non-coding RNA, linked to hereditary or inborn limb defects. We also discuss the role of chromatin organisation and enhancer-promoter interactions in the aetiology of limb malformations.

A clinical review and introduction of the diagnostic algorithm for thalidomide embryopathy (DATE)

Thalidomide embryopathy results from the ingestion of thalidomide in the first trimester during pregnancy, causing multiple forms of congenital abnormalities of variable severity that involve all systems. The skeletal findings most frequently affect the limbs, particularly the upper limbs and hands. Increasingly, several genetic disorders with similar birth defects have been identified. New cases of malformations owing to possible exposure to thalidomide continue to present through both historical and current usage. However, inadequate proof of ingestion, marked phenotypic variation and the possibility of an alternative genetic condition, hinder the diagnosis of thalidomide embryopathy. We introduce a 'diagnostic algorithm for thalidomide embryopathy' (DATE) diagnostic software that can potentially provide a numerical score for the likelihood of birth defects in an individual as being caused by exposure to thalidomide and to provide a differential diagnosis based on the pattern of malformation.

Clinical Genetics of Polydactyly: An Updated Review

Polydactyly, also known as hyperdactyly or hexadactyly is the most common hereditary limb anomaly characterized by extra fingers or toes, with various associated morphologic phenotypes as part of a syndrome (syndromic polydactyly) or may occur as a separate event (non-syndromic polydactyly). Broadly, the non-syndromic polydactyly has been classified into three types, i.e.; preaxial polydactyly (radial), central polydactyly (axial), and postaxial polydactyly (ulnar). Mostly inherited as an autosomal dominant entity with variable penetrance and caused by defects that occur in the anterior-posterior patterning of limb development. In humans, to-date at least 10 loci and six genes causing non-syndromic polydactyly have been identified, including the ZNF141, GLI3, MIPOL1, IQCE, PITX1, and the GLI1. In the present review, clinical, genetic and molecular characterization of the polydactyly types has been presented including the recent genes and loci identified for non-syndromic polydactyly. This review provides an overview of the complex genetic mechanism underlie polydactyly and might help in genetic counseling and quick molecular diagnosis.

Early Gestational Hypoxia and Adverse Developmental Outcomes

Hypoxia is a normal and essential part of embryonic development. However, this state may leave the embryo vulnerable to damage when oxygen supply is disturbed. Embryofetal response to hypoxia is dependent on duration and depth of hypoxia, as well as developmental stage. Early postimplantation rat embryos were resilient to hypoxia, with many surviving up to 1.5 hr of uterine clamping, while most mid-gestation embryos were dead after 1 hour of clamping. Survivors were small and many had a range of defects, principally terminal transverse limb reduction defects. Similar patterns of malformations occurred when embryonic hypoxia was induced by maternal hypoxia, interruption of uteroplacental flow, or perfusion and embryonic bradycardia. There is good evidence that high altitude pregnancies are associated with smaller babies and increased risk of some malformations, but these results are complicated by increased risk of pre-eclampsia. Early onset pre-eclampsia itself is associated with small for dates and increased risk of atrio-ventricular septal defects. Limb defects have clearly been associated with chorionic villus sampling, cocaine, and misoprostol use. Similar defects are also observed with increased frequency among fetuses who are homozygous for thalassemia. Drugs that block the potassium current, whether as the prime site of action or as a side effect, are highly teratogenic in experimental animals. They induce embryonic bradycardia, hypoxia, hemorrhage, and blisters, leading to transverse limb defects as well as craniofacial and cardiovascular defects. While evidence linking these drugs to birth defects in humans is not compelling, the reason may methodological rather than biological. Birth Defects Research 109:1358-1376, 2017.© 2017 Wiley Periodicals, Inc.

IRF6 expression in basal epithelium partially rescues Irf6 knockout mice

BACKGROUND

Mutations in IRF6, CHUK (IKKA), and RIPK4 can lead to a disease spectrum that includes cutaneous, limb, and craniofacial malformations. Loss of these alleles in the mouse leads to perinatal lethality and severe cutaneous, limb, and craniofacial defects also. Genetic rescue in the mouse has been shown for Ikka and Ripk4.

RESULTS

Here, we show partial genetic rescue of Irf6 knockout embryos using the KRT14 promoter to drive Irf6 expression in the basal epithelium. In contrast to Irf6 knockout embryos, rescue embryos survive the immediate perinatal period. Macroscopic examination reveals rescue of skin adhesions between the axial and appendicular skeleton. Unexpectedly, KRT14-driven Irf6 expression does not completely rescue orofacial clefting and adhesions between the palate and tongue, suggesting the importance of cell-autonomous IRF6 expression in periderm. Like knockout embryos, Irf6 rescue embryos also have persistent esophageal adhesions, which likely contribute to postnatal demise.

CONCLUSIONS

Together, these data suggest that targeted expression of IRF6 can significantly reduce disease severity, but that a minimum level of Irf6 in both periderm and basal epithelial cells is necessary for orofacial development. Therefore, homologous human and mouse phenotypes are observed for IRF6, IKKA, and RIPK4. In this work, we show that altering the expression level of IRF6 dramatically modified this phenotype in utero. Developmental Dynamics 246:670-681, 2017. © 2017 Wiley Periodicals, Inc.

Cornelia de Lange syndrome: To diagnose or not to diagnose in utero?

Cornelia de Lange syndrome (CdLS) is an inherited condition with a wide spectrum of phenotypic anomalies, consisting mainly of growth impairment, multi-organ abnormalities, and neurocognitive delay. Clinical diagnostic criteria after birth are well defined, whereas when to suspect the syndrome during intrauterine life still remains undefined. This review summarizes the main possible prenatal findings in CdLS, suggesting that a skilled ultrasound scan in cases of intrauterine growth restriction associated with other fetal abnormalities may improve the chance of prenatal diagnosis of CdLS, especially in families known to be at high risk. We propose that, following a sequence of detailed scans and examinations, CdLS affected fetuses could be diagnosed in utero, when one or more conditions (among them, intrauterine growth restriction, limb defects, facial abnormalities, diaphragmatic hernia, and heart diseases) are detected, and possibly confirmed by specific molecular testing. Birth Defects Research 109:771-777, 2017. © 2017 The Authors. Birth Defects Research Published by Wiley Periodicals, Inc.

Cases of limb-body wall complex: Early amnion rupture, vascular disruption, or abnormal splitting of the embryo?

We report two cases of limb-body wall complex (LBWC), also known as body stalk anomaly, a rare form of body wall defect incompatible with life. The first case was identified during a level II ultrasound examination performed at 7 wk gestational age. The delivery was by breech extraction at 39 wk and 4 days. The second case was delivered by spontaneous vaginal delivery at 35 wk and 5 days. Karyotype analysis was normal in both fetuses. The phenotype of LBWC is variable, but commonly identified features include: exencephaly, limb defects, and either facial clefts or thoraco-abdominoschisis. The exact etiology remains uncertain, as the disorder has been regarded as sporadic with low recurrence. Vascular disruption during early embryogenesis, early amnion rupture, abnormal splitting of the embryo, and failure of amnion fusion have been implicated in the pathogenesis of LBWC. A role for possible gene mutation and maternal use of alcohol, tobacco, or illicit drugs has also been suggested. Detailed ultrasonography along with biochemical screening may allow for early detection.

Characterization of limb differences in children with Cornelia de Lange Syndrome

Cornelia de Lange syndrome (CdLS) is a well-described multisystem developmental disorder characterized by dysmorphic facial features, growth and behavioral deficits, and cardiac, gastrointestinal, and limb anomalies. The limb defects seen in CdLS can be mild, with small feet or hands only, or can be severe, with variable deficiency defects involving primarily the ulnar structures and ranging from mild hypoplasia of the fifth digit to complete absence of the forearm. Interestingly, the upper limbs are typically much more involved than the lower extremities that generally manifest with small feet and 2-3 syndactyly of the toes and shortened fourth metatarsal. The upper limbs often manifest asymmetric involvement. The limb findings in our cohort of 378 individuals with CdLS demonstrate a consistent pattern of laterality and symmetry involvement (with increased severity of right-sided limb in individuals with asymmetric limb defects) and a correlation of more significant limb defects with an increased risk of other structural anomalies, and more severe behavioral outcomes. Additionally, we found that individuals with mutations in NIPBL were most likely to have limb defects compared to mutations in other genes with nonsense, exonic deletion, and frameshift mutations being most prevalent in those with limb defects. Characterization of the limb differences in children with CdLS may provide a tool to assist in genetic counseling and determining prognosis. This paper will review the limb involvement in a large cohort of individuals with CdLS assessing the correlation with molecular etiologies, symmetry, additional structural birth defects, and cognitive outcomes. © 2016 Wiley Periodicals, Inc.

GLI3 mutations in syndromic and non-syndromic polydactyly in two Indian families

The GLI3 protein is a zinc finger transcription factor, expressed early in development. The GLI3 gene exhibits allelic heterogeneity as mutations in this gene are associated with several developmental syndromic and non-syndromic polydactyly. The present study reports two cases: first, a familial case of Greig Cephalopolysyndactyly Syndrome (GCPS); the second is a sporadic case with both postaxial polydactyly (PAP) type A and B. Resequencing of GLI3 gene reveals a previously reported nonsense truncation mutation g.42007251G > A (p.R792X; rs121917714) in the GCPS family and a novel single nucleotide insertion g.42004239_42004240insA (p.E1478X) in the sporadic case of postaxial polydactyly (PAP). Both nonsense truncation mutations; p.R792X (GCPS) and p.E1478X (PAP) introduce a premature stop codon leading to loss of C-terminal domains.

Clinical and genetic characteristics of craniosynostosis in Hungary

Craniosynostosis, the premature closure of cranial sutures, is a common craniofacial disorder with heterogeneous etiology and appearance. The purpose of this study was to investigate the clinical and molecular characteristics of craniosynostoses in Hungary, including the classification of patients and the genetic analysis of the syndromic forms. Between 2006 and 2012, 200 patients with craniosynostosis were studied. Classification was based on the suture(s) involved and the associated clinical features. In syndromic cases, genetic analyses, including mutational screening of the hotspot regions of the FGFR1, FGFR2, FGFR3, and TWIST1 genes, karyotyping and FISH study of TWIST1, were performed. The majority (88%) of all patients with craniosynostosis were nonsyndromic. The sagittal suture was most commonly involved, followed by the coronal, metopic, and lambdoid sutures. Male, twin gestation, and very low birth weight were risk factors for craniosynostosis. Syndromic craniosynostosis was detected in 24 patients. In 17 of these patients, Apert, Crouzon, Pfeiffer, Muenke, or Saethre-Chotzen syndromes were identified. In one patient, multiple-suture craniosynostosis was associated with achondroplasia. Clinical signs were not typical for any particular syndrome in six patients. Genetic abnormalities were detected in 18 syndromic patients and in 8 relatives. In addition to 10 different, known mutations in FGFR1,FGFR2 or FGFR3, one novel missense mutation, c.528C>G(p.Ser176Arg), was detected in the TWIST1 gene of a patient with Saethre-Chotzen syndrome. Our results indicate that detailed clinical assessment is of paramount importance in the classification of patients and allows indication of targeted molecular testing with the highest possible diagnostic yield.

An allelic series of Trp63 mutations defines TAp63 as a modifier of EEC syndrome

Human Ectrodactyly, Ectodermal dysplasia, Clefting (EEC) syndrome is an autosomal dominant developmental disorder defined by limb deformities, skin defects, and craniofacial clefting. Although associated with heterozygous missense mutations in TP63, the genetic basis underlying the variable expressivity and incomplete penetrance of EEC is unknown. Here, we show that mice heterozygous for an allele encoding the Trp63 p.Arg318His mutation, which corresponds to the human TP63 p.Arg279His mutation found in patients with EEC, have features of human EEC. Using an allelic series, we discovered that whereas clefting and skin defects are caused by loss of Trp63 function, limb anomalies are due to gain- and/or dominant-negative effects of Trp63. Furthermore, we identify TAp63 as a strong modifier of EEC-associated phenotypes with regard to both penetrance and expressivity.

Adams-Oliver Syndrome. A case with isolated aplasia cutis congenita and skeletal defects

BACKGROUND

Adams-Oliver Syndrome is characterized by the combination of aplasia cutis congenita and limb anomalies. It was initially described in 1945 by Adams and Oliver.

MAIN OBSERVATIONS

We report a case of a 10-year-old girl with Adams-Oliver Syndrome with aplasia cutis congenita and limb defects only with no internal organ anomalies.

CONCLUSIONS

Adams-Oliver Syndrome is a rare multisystem disorder of unknown etiology. It may be presented by isolated aplasia cutis congenita and limb anomalies.