Familial microduplication of 17q23.1-q23.2 involving TBX4 is associated with congenital clubfoot and reduced penetrance in females

COL1A1 regulates the apoptosis of embryonic stem cells by mediating the PITX1/TBX4 signaling

PURPOSE

The purpose of this study is to explore the regulatory function of COL1A1 against the apoptosis of embryonic stem cells (ESCs) and the potential function in congenital talipes equinovarus (CTEV).

METHODS

Muscle tissues were collected from 20 children with CTEV and 20 children without CTEV, followed by detecting the expression of COL1A1 using the RT-PCR method. COL1A1 was knocked down in H1 and H9 human ESCs using the RNA interference technology, followed by determining the level of COL1A1, PITX1, TBX4, HOXD10, Fas, FasL, and Bax using the Western blotting assay.

RESULTS

COL1A1 was found markedly upregulated in muscle tissues of CTEV children. In H1 and H9 human ESCs, compared to the empty vector, COL1A1, PITX1, TBX4, HOXD10, Fas, FasL, and Bax were found notably downregulated after transfected with the siRNA targeting COL1A1.

CONCLUSION

COL1A1 induced the apoptosis of ESCs by mediating the PITX1/TBX4 signaling and might be a potential target for treating CTEV.

Prenatal diagnosis and genetic etiology analysis of talipes equinovarus by chromosomal microarray analysis

BACKGROUND

With the advancement of molecular technology, fetal talipes equinovarus (TE) is believed to be not only associated with chromosome aneuploidy, but also related to chromosomal microdeletion and microduplication. The study aimed to explore the molecular etiology of fetal TE and provide more information for the clinical screening and genetic counseling of TE by Chromosomal Microarray Analysis (CMA).

METHODS

This retrospectively study included 131 fetuses with TE identified by ultrasonography. Conventional karyotyping and SNP array analysis were performed for all the subjects. They were divided into isolated TE group (n = 55) and complex group (n = 76) according to structural anomalies.

RESULTS

Among the total of 131 fetuses, karyotype analysis found 12(9.2%) abnormal results, while SNP array found 27 (20.6%) cases. Trisomy 18 was detected most frequently among abnormal karyotypes. The detection rate of SNP array was significantly higher than that of traditional chromosome karyotype analysis (P < 0.05). SNP array detected 15 (11.5%) cases of submicroscopic abnormalities that karyotype analysis did not find. The most common CNV was the 22q11.2 microdeletion. For both analyses, the overall detection rates were significantly higher in the complex TE group than in the isolated TE group (karyotype: P < 0.05; SNP array: P < 0.05). The incremental yield of chromosomal abnormalities in fetuses with unilateral TE (22.0%) was higher than in fetuses with bilateral TE (19.8%), but this difference was not statistically significant (P > 0.05). Abnormal chromosomes were most frequently detected in fetuses with TE plus cardiovascular system abnormalities.

CONCLUSION

Fetal TE is related to chromosomal microdeletion or microduplication. Prenatal diagnosis is recommended for fetuses with TE, and CMA testing is preferred. CMA can improve the detection rate of chromosomal abnormalities associated with fetal TE, especially in pregnancies with complex TE.

Incidence and prevalence of congenital clubfoot in Apulia: a regional model for future prospective national studies

BACKGROUND

Congenital clubfoot is a fairly common and severe congenital malformation, most often of idiopathic origin. A smaller percentage of cases is related to chromosomal abnormalities and genetic syndromes. It is estimated that 0.5/1000 newborns are affected worldwide, with a male to female ratio of 2:1 and greater distribution in developing countries (80%). The "European Surveillance of Congenital Anomalies (EUROCAT)" reported clubfoot prevalence in European newborns, but data regarding Italy are missing or poor. We aim to provide detailed data on clubfoot incidence according to the Apulian Regional Registry on Congenital Malformations and to report current knowledge on clubfoot genetic factors.

METHODS

We extrapolated data from the Regional Registry of Congenital Malformations to evaluate incidence and prevalence of congenital clubfoot in Apulia, Italy over a period of four years (2015-2018). We also performed a narrative review focusing on genetic mutations leading to congenital clubfoot.

RESULTS

Over the period from 2015 to 2018 in Apulia, Italy, 124,017 births were recorded and 209 cases of clubfoot were found, accounting for an incidence rate of 1.7/1,000 and a prevalence rate of 1.6/1,000. Six families of genes have been reported to have an etiopathogenetic role on congenital clubfoot.

CONCLUSIONS

Incidence and prevalence of congenital clubfoot in Apulia, Italy, are comparable with those reported in the other Italian regions but higher than those reported in previous studies from Europe. Genetic studies to better classify congenital clubfoot in either syndromic or isolated forms are desirable.

Molecular Function and Contribution of TBX4 in Development and Disease

Over the past decade, recognition of the profound impact of the TBX4 (T-box 4) gene, which encodes a member of the evolutionarily conserved family of T-box-containing transcription factors, on respiratory diseases has emerged. The developmental importance of TBX4 is emphasized by the association of TBX4 variants with congenital disorders involving respiratory and skeletal structures; however, the exact role of TBX4 in human development remains incompletely understood. Here, we discuss the developmental, tissue-specific, and pathological TBX4 functions identified through human and animal studies and review the published TBX4 variants resulting in variable disease phenotypes. We also outline future research directions to fill the gaps in our understanding of TBX4 function and of how TBX4 disruption affects development.

What Is the Exact Contribution of PITX1 and TBX4 Genes in Clubfoot Development? An Italian Study

Congenital clubfoot is a common pediatric malformation that affects approximately 0.1% of all births. 80% of the cases appear isolated, while 20% can be secondary or associated with complex syndromes. To date, two genes that appear to play an important role are PTIX1 and TBX4, but their actual impact is still unclear. Our study aimed to evaluate the prevalence of pathogenic variants in PITX1 and TBX4 in Italian patients with idiopathic clubfoot. PITX1 and TBX4 genes were analyzed by sequence and SNP array in 162 patients. We detected only four nucleotide variants in TBX4, predicted to be benign or likely benign. CNV analysis did not reveal duplications or deletions involving both genes and intragenic structural variants. Our data proved that the idiopathic form of congenital clubfoot was rarely associated with mutations and CNVs on PITX1 and TBX4. Although in some patients, the disease was caused by mutations in both genes; they were responsible for only a tiny minority of cases, at least in the Italian population. It was not excluded that other genes belonging to the same TBX4-PITX1 axis were involved, even if genetic complexity at the origin of clubfoot required the involvement of other factors.

The molecular genetics of human appendicular skeleton

Disorders that result from de-arrangement of growth, development and/or differentiation of the appendages (limbs and digit) are collectively called as inherited abnormalities of human appendicular skeleton. The bones of appendicular skeleton have central role in locomotion and movement. The different types of appendicular skeletal abnormalities are well described in the report of "Nosology and Classification of Genetic skeletal disorders: 2019 Revision". In the current article, we intend to present the embryology, developmental pathways, disorders and the molecular genetics of the appendicular skeletal malformations. We mainly focused on the polydactyly, syndactyly, brachydactyly, split-hand-foot malformation and clubfoot disorders. To our knowledge, only nine genes of polydactyly, five genes of split-hand-foot malformation, nine genes for syndactyly, eight genes for brachydactyly and only single gene for clubfoot have been identified to be involved in disease pathophysiology. The current molecular genetic data will help life sciences researchers working on the rare skeletal disorders. Moreover, the aim of present systematic review is to gather the published knowledge on molecular genetics of appendicular skeleton, which would help in genetic counseling and molecular diagnosis.

Genotype-phenotype correlation in clubfoot (talipes equinovarus)

Clubfoot (talipes equinovarus) is a congenital malformation affecting muscles, bones, connective tissue and vascular or neurological structures in limbs. It has a complex aetiology, both genetic and environmental. To date, the most important findings in clubfoot genetics involve PITX1 variants, which were linked to clubfoot phenotype in mice and humans. Additionally, copy number variations encompassing TBX4 or single nucleotide variants in HOXC11, the molecular targets of the PITX1 transcription factor, were linked to the clubfoot phenotype. In general, genes of cytoskeleton and muscle contractile apparatus, as well as components of the extracellular matrix and connective tissue, are frequently linked with clubfoot aetiology. Last but not least, an equally important element, that brings us closer to a better understanding of the clubfoot genotype/phenotype correlation, are studies on the two known animal models of clubfoot-the pma or EphA4 mice. This review will summarise the current state of knowledge of the molecular basis of this congenital malformation.

Congenital Abdominal Wall Defects: A Topic Review and a Case Report of a Lethal Polymalformation Syndrome with a Giant Abdominoschisis

Abdominal wall defects (AWDs) represent a wide spectrum of congenital anomalies which are characterized by a herniation of abdominal organs through a pathologic opening in the abdominal region. The author describes a 29-year-old pregnant woman who was prenatally found to have a living female fetus with a giant omphalocele and a spinal deformation in the lumbosacral region. An evisceration of the abdominal contents into the amnionic cavity was visible. Based on USG findings the limb-body wall complex was suggested. An amniocentesis was performed and a genetic testing identified a chromosome 17q23.1–q23.2 duplication. As the fetal anomaly was considered incompatible with life, a medical termination of the pregnancy was carried out. Postmortem examination of the fetus revealed a huge abdominoschisis with a complete evisceration of the liver, stomach, small and large intestines, spleen, and the right kidney. A severe left-sided scoliosis deformity of the spine with crooked trunk was evident. The gross findings shared the features of omphalocele and limb-body wall complex with no postnatal life expectancy. Most fetal AWDs have poor prognosis. The pathology of these conditions differ greatly and require specific prenatal evaluation and pregnancy management for each entity. Accurate assessment of AWDs will allow the identification of isolated forms with better clinical outcomes compared to associated multiple malformations with chromosomal anomalies or genetic syndromes.

Integrated Bioinformatics Analysis Reveals Potential Pathway Biomarkers and Their Interactions for Clubfoot

Background

Congenital talipes equinovarus (clubfoot), one of the most regular pediatric congenital skeletal anomalies, seriously affects the normal growth and development of about 1 in 1000 newborns. Although it has been investigated widely, the etiology and pathogenesis of clubfoot are still controversial.

Material/Methods

g: Profiler, NetworkAnalyst and WebGestalt were used to probe the enriched signaling pathways by using the Gene Ontology (GO), Human Phenotype Ontology (HP), Kyoto Encyclopedia of Genes and Genomes (KEGG), Reactome (REAC), and WikiPathways (WP) databases. Large numbers of enriched signaling pathways were identified using the integrated bioinformatics enrichment analyses.

Results

Apoptosis or programmed cell death (PCD), disease, muscle contraction, metabolism, and immune system were the top functions. Embryo or organ morphogenesis and development, cell or muscle contraction, and apoptosis were the top biological processes, and cell/muscle contraction and apoptosis were the top molecular functions using enriched GO terms analysis. There were a large number of complex interactions in the genes, enriched pathways, and transcription factor (TF)-miRNA co-regulatory networks. Transcription factors such as FOXN3, GLI3, HOX, and NCOR2 family regulated the gene expression of APAF1, BCL2, BID, CASP, MTHFR, and TPM family.

Conclusions

The results of bioinformatics enrichment analysis not only supported the previously proposed hypotheses, e.g., extracellular matrix (ECM) abnormality, fetal movement reducing, genetic abnormality, muscle abnormality, neurological abnormality, skeletal abnormality and vascular abnormality, but also indicated that cellular or immune responses to external stimulus, molecular transport and metabolism may be new etiological mechanisms in clubfoot.

Rare and de novo duplications containing SHOX in clubfoot

Introduction

Congenital clubfoot is a common birth defect that affects at least 0.1% of all births. Nearly 25% cases are familial and the remaining are sporadic in inheritance. Copy number variants (CNVs) involving transcriptional regulators of limb development, including PITX1 and TBX4, have previously been shown to cause familial clubfoot, but much of the heritability remains unexplained.

Methods

Exome sequence data from 816 unrelated clubfoot cases and 2645 in-house controls were analysed using coverage data to identify rare CNVs. The precise size and location of duplications were then determined using high-density Affymetrix Cytoscan chromosomal microarray (CMA). Segregation in families and de novo status were determined using qantitative PCR.

Results

Chromosome Xp22.33 duplications involving SHOX were identified in 1.1% of cases (9/816) compared with 0.07% of in-house controls (2/2645) (p=7.98×10⁻⁵, OR=14.57) and 0.27% (38/13592) of Atherosclerosis Risk in Communities/the Wellcome Trust Case Control Consortium 2 controls (p=0.001, OR=3.97). CMA validation confirmed an overlapping 180.28 kb duplicated region that included SHOX exons as well as downstream non-coding regions. In four of six sporadic cases where DNA was available for unaffected parents, the duplication was de novo. The probability of four de novo mutations in SHOX by chance in a cohort of 450 sporadic clubfoot cases is 5.4×10^–10.

Conclusions

Microduplications of the pseudoautosomal chromosome Xp22.33 region (PAR1) containing SHOX and downstream enhancer elements occur in ~1% of patients with clubfoot. SHOX and regulatory regions have previously been implicated in skeletal dysplasia as well as idiopathic short stature, but have not yet been reported in clubfoot. SHOX duplications likely contribute to clubfoot pathogenesis by altering early limb development.

Homozygous Null TBX4 Mutations Lead to Posterior Amelia with Pelvic and Pulmonary Hypoplasia

The development of hindlimbs in tetrapod species relies specifically on the transcription factor TBX4. In humans, heterozygous loss-of-function TBX4 mutations cause dominant small patella syndrome (SPS) due to haploinsufficiency. Here, we characterize a striking clinical entity in four fetuses with complete posterior amelia with pelvis and pulmonary hypoplasia (PAPPA). Through exome sequencing, we find that PAPPA syndrome is caused by homozygous TBX4 inactivating mutations during embryogenesis in humans. In two consanguineous couples, we uncover distinct germline TBX4 coding mutations, p.Tyr113^∗ and p.Tyr127Asn, that segregated with SPS in heterozygous parents and with posterior amelia with pelvis and pulmonary hypoplasia syndrome (PAPPAS) in one available homozygous fetus. A complete absence of TBX4 transcripts in this proband with biallelic p.Tyr113^∗ stop-gain mutations revealed nonsense-mediated decay of the endogenous mRNA. CRISPR/Cas9-mediated TBX4 deletion in Xenopus embryos confirmed its restricted role during leg development. We conclude that SPS and PAPPAS are allelic diseases of TBX4 deficiency and that TBX4 is an essential transcription factor for organogenesis of the lungs, pelvis, and hindlimbs in humans.

Transcriptomics analysis revealing candidate genes and networks for sex differentiation of yesso scallop (Patinopecten yessoensis)

Background

The Yesso scallop, Patinopecten (Mizuhopecten) yessoensis, is a commercially important bivalve in the coastal countries of Northeast Asia. It has complex modes of sex differentiation, but knowledge of the mechanisms underlying this sex determination and differentiation is limited.

Results

In this study, the gonad tissues from females and males at three developmental stages were used to investigate candidate genes and networks for sex differentiation via RNA-Req. A total of 901,980,606 high quality clean reads were obtained from 18 libraries, of which 417 expressed male-specific genes and 754 expressed female-specific genes. Totally, 10,074 genes differentially expressed in females and males were identified. Weighted gene co-expression network analysis (WGCNA) revealed that turquoise and green gene modules were significantly positively correlated with male gonads, while coral1 and black modules were significantly associated with female gonads. The most important gene for sex determination and differentiation was Pydmrt 1, which was the only gene discovered that determined the male sex phenotype during early gonadal differentiation. Enrichment analyses of GO terms and KEGG pathways revealed that genes involved in metabolism, genetic and environmental information processes or pathways are sex-biased. Forty-nine genes in the five modules involved in sex differentiation or determination were identified and selected to construct a gene co-expression network and a hypothesized sex differentiation pathway.

Conclusions

The current study focused on screening genes of sex differentiation in Yesso scallop, highlighting the potential regulatory mechanisms of gonadal development in P. yessoensis. Our data suggested that WCGNA can facilitate identification of key genes for sex differentiation and determination. Using this method, a hypothesized P. yessoensis sex determination and differentiation pathway was constructed. In this pathway, Pydmrt 1 may have a leading function.

Electronic supplementary material

The online version of this article (10.1186/s12864-019-6021-6) contains supplementary material, which is available to authorized users.

The genetics of isolated and syndromic clubfoot

PURPOSE

Congenital clubfoot is a serious birth defect that affects nearly 0.1% of all births. Though there is strong evidence for a genetic basis of isolated clubfoot, aside from a handful of associations, much of the heritability remains unexplained.

METHODS

By systematically examining the genes involved in syndromic clubfoot, we may find new candidate genes and pathways to investigate in isolated clubfoot.

RESULTS

In addition to the expected enrichment of extracellular matrix and transforming growth factor beta (TGF-β) signalling genes, we find many genes involved in syndromic clubfoot encode peroxisomal matrix proteins, as well as enzymes necessary for sulfation of proteoglycans, an important part of connective tissue. Further, the association of Filamin B with isolated clubfoot as well as syndromic clubfoot is an encouraging finding.

CONCLUSION

We should examine these categories for enrichment in isolated clubfoot patients to increase our understanding of the underlying biology and pathophysiology of this deformity. Understanding the spectrum of syndromes that have clubfoot as a feature enables a better understanding of the underlying pathophysiology of the disorder and directs future genetic screening efforts toward certain genes and genetic pathways.

LEVEL OF EVIDENCE

V.

Abnormal expression of TBX4 during anorectal development in rat embryos with ethylenethiourea-induced anorectal malformations

BACKGROUND

To assess the expression of T-box transcription factor 4 (TBX4) during the anorectal development in normal and ethylenethiourea (ETU)-induced anorectal malformations (ARM) rat embryos.

METHODS

Anorectal malformations was induced by ETU on the 10th gestational day (E10) in rat embryos. Spatio-temporal expression of TBX4 was evaluated in normal (n = 490) and ETU-induced ARM rat embryos (n = 455) from E13 to E16 by immunohistochemical staining, Western blot analysis and real-time RT-PCR.

RESULTS

In the normal embryos, immunohistochemical staining revealed that TBX4 expression was detected in the epithelium of hindgut and urorectal septum (URS) on E13. TBX4-immunopositive cells were increased significantly in the epithelium of hindgut and URS, the future anal orifice part of cloacal membrane on E14. On E15, abundant stained cells were observed in the rectum, URS and dorsal cloacal membrane and the expression of positive cells reached its peak. On E16, only sporadic positive cells were distributed in the epithelium of the distal rectum. In the ARM embryos, the hindgut/rectum, URS and dorsal cloacal membrane were faint for TBX4 immunohistochemical staining. In the normal group, TBX4 protein and mRNA expression showed time-dependent changes in the hindgut/rectum from E13 to E16 on Western blot and real-time RT-PCR. On E13 and E15, the expression level of TBX4 mRNA in the ARM group was significantly lower than that in the normal group (P < 0.05). On E15, the expression level of TBX4 protein in the ARM group was significantly lower than that in the normal group (P < 0.05).

CONCLUSIONS

The expression of TBX4 was downregulated in ETU-induced ARM embryos, which may play important roles in the pathogenesis of anorectal development.

Neonatal Lung Disease Associated with TBX4 Mutations

Variable lung disease was documented in 2 infants with heterozygous TBX4 mutations; their clinical presentations, pathology, and outcomes were distinct. These findings demonstrate that TBX4 gene mutations are associated with neonatal respiratory failure and highlight the wide spectrum of clinicopathological outcomes that have implications for patient diagnosis and management.

The etiology of idiopathic congenital talipes equinovarus: a systematic review

Background

Also known as clubfoot, idiopathic congenital talipes equinovarus (ICTEV) is the most common pediatric deformity and occurs in 1 in every 1000 live births. Even though it has been widely researched, the etiology of ICTEV remains poorly understood and is often described as being based on a multifactorial genesis. Genetic and environmental factors seem to have a major role in the development of this disease. Thus, the aim of this review is to analyze the available literature to document the current evidence on ICTEV etiology.

Methods

The literature on ICTEV etiology was systematically reviewed using the following inclusion criteria: studies of any level of evidence, reporting clinical or preclinical results, published in the last 20 years (1998–2018), and dealing with the etiology of ICTEV.

Results

A total of 48 articles were included. ICTEV etiology is still controversial. Several hypotheses have been researched, but none of them are decisive. Emerging evidence suggests a role of several pathways and gene families associated with limb development (HOX family; PITX1-TBX4), the apoptotic pathway (caspases), and muscle contractile protein (troponin and tropomyosin), but a major candidate gene has still not been identified. Strong recent evidence emerging from twin studies confirmed major roles of genetics and the environment in the disease pathogenesis.

Conclusions

The available literature on the etiology of ICTEV presents major limitations in terms of great heterogeneity and a lack of high-profile studies. Although many studies focus on the genetic background of the disease, there is lack of consensus on one or multiple targets. Genetics and smoking seem to be strongly associated with ICTEV etiology, but more studies are needed to understand the complex and multifactorial genesis of this common congenital lower-limb disease.

Familial impairment of vocal cord mobility in childhood with clubfoot

We report on a family with three siblings, male and female, affected by congenital bilateral limitation of vocal cord abduction, with the additional finding of clubfeet in two. The paternal family history suggests an autosomal dominant inheritance. The siblings and father also have mild craniofacial features, which may be an expression of variability or may be unrelated. The association between congenital vocal cord paralysis and clubfeet has been reported with additional major features or in the context of Charcot-Marie-Tooth disease. However, the two in isolation have only been reported in one other family previously. Genomic analyses of the family, including chromosomal microarray and exome sequencing, showed neither a likely pathogenic variant in a known disease gene nor a compelling candidate gene variant. We propose that the association of these two findings constitutes a novel recognizable phenotype, for which a genetic cause remains undetermined.

The developmental and genetic basis of 'clubfoot' in the peroneal muscular atrophy mutant mouse

Genetic factors underlying the human limb abnormality congenital talipes equinovarus ('clubfoot') remain incompletely understood. The spontaneous autosomal recessive mouse 'peroneal muscular atrophy' mutant (PMA) is a faithful morphological model of human clubfoot. In PMA mice, the dorsal (peroneal) branches of the sciatic nerves are absent. In this study, the primary developmental defect was identified as a reduced growth of sciatic nerve lateral motor column (LMC) neurons leading to failure to project to dorsal (peroneal) lower limb muscle blocks. The pma mutation was mapped and a candidate gene encoding LIM-domain kinase 1 (Limk1) identified, which is upregulated in mutant lateral LMC motor neurons. Genetic and molecular analyses showed that the mutation acts in the EphA4-Limk1-Cfl1/cofilin-actin pathway to modulate growth cone extension/collapse. In the chicken, both experimental upregulation of Limk1 by electroporation and pharmacological inhibition of actin turnover led to defects in hindlimb spinal motor neuron growth and pathfinding, and mimicked the clubfoot phenotype. The data support a neuromuscular aetiology for clubfoot and provide a mechanistic framework to understand clubfoot in humans.

Genetics of clubfoot; recent progress and future perspectives

Clubfoot or talipes equinovarus (TEV) is an inborn three-dimensional deformity of leg, ankle and foot. It results from structural defects of several tissues of foot and lower leg leading to abnormal positioning of foot and ankle joints. TEV can lead to long-lasting functional disability, malformation and discomfort if left untreated. Substantial progress has been achieved in the management and diagnosis of limb defects; however, not much is known about the molecular players and signalling pathways underlying TEV disorder. The homeostasis and development of the limb depends on the complex interactions between the lateral plate mesoderm cells and outer ectoderm. These complex interactions include HOX signalling and PITX1-TBX4 pathways. The susceptibility to develop TEV is determined by a number of environmental and genetic factors, although the nature and level of interplay between them remains unclear. Familial occurrence and inter and intra phenotypic variability of TEV is well documented. Variants in genes that code for contractile proteins of skeletal myofibers might play a role in the aetiology of TEV but, to date, no strong candidate genes conferring increased risk have emerged, although variants in TBX4, PITX1, HOXA, HOXC and HOXD clusters genes, NAT2 and others have been shown to be associated with TEV. The mechanisms by which variants in these genes confer risk and the nature of the physical and genetic interaction between them remains to be determined. Elucidation of genetic players and cellular pathways underlying TEV will certainly increase our understanding of the pathophysiology of this deformity.

The 2017 ABJS Nicolas Andry Award: Advancing Personalized Medicine for Clubfoot Through Translational Research

BACKGROUND

Clubfoot is one of the most common pediatric orthopaedic disorders. While the Ponseti method has revolutionized clubfoot treatment, it is not effective for all patients. When the Ponseti method does not correct the foot, patients are at risk for lifelong disability and may require more-extensive surgery.

QUESTIONS/PURPOSES

(1) What genetic and morphologic abnormalities contribute to the development of clubfoot? (2) How can this information be used to devise personalized treatment paradigms for patients with clubfoot?

METHODS

Human gene sequencing, molecular genetic engineering of mouse models of clubfoot, MRI of clubfoot, and development of new treatment methods all have been used by our group to understand the biological basis and improve therapy for this group of disorders.

RESULTS

We gained new insight into clubfoot pathogenesis from our discovery that mutations in the PITX1-TBX4-HOXC transcriptional pathway cause familial clubfoot and vertical talus in a small number of families, with the unique lower limb expression of these genes providing an explanation for the lack of upper extremity involvement in these disorders. MRI studies revealed corresponding morphologic abnormalities, including hypomorphic muscle, bone, and vasculature, that are not only associated with these gene mutations, but also are biomarkers for treatment-resistant clubfoot.

CONCLUSIONS

Based on an understanding of the underlying biology, we improved treatment methods for neglected and syndromic clubfoot, developed new treatment for congenital vertical talus based on the principles of the Ponseti method, and designed a new dynamic clubfoot brace to improve strength and compliance.

T-Box Genes in Human Development and Disease

T-box genes are important development regulators in vertebrates with specific patterns of expression and precise roles during embryogenesis. They encode transcription factors that regulate gene transcription, often in the early stages of development. The hallmark of this family of proteins is the presence of a conserved DNA binding motif, the "T-domain." Mutations in T-box genes can cause developmental disorders in humans, mostly due to functional deficiency of the relevant proteins. Recent studies have also highlighted the role of some T-box genes in cancer and in cardiomyopathy, extending their role in human disease. In this review, we focus on ten T-box genes with a special emphasis on their roles in human disease.

Deletions of 5' HOXC genes are associated with lower extremity malformations, including clubfoot and vertical talus

BACKGROUND

Deletions of the HOXC gene cluster result in variable phenotypes in mice, but have been rarely described in humans.

OBJECTIVE

To report chromosome 12q13.13 microdeletions ranging from 13 to 175 kb and involving the 5' HOXC genes in four families, segregating congenital lower limb malformations, including clubfoot, vertical talus and hip dysplasia.

METHODS

Probands (N=253) with clubfoot or vertical talus were screened for point mutations and copy number variants using multiplexed direct genomic selection, a pooled BAC targeted capture approach. SNP genotyping included 1178 probands with clubfoot or vertical talus and 1775 controls.

RESULTS

The microdeletions share a minimal non-coding region overlap upstream of HOXC13, with variable phenotypes depending upon HOXC13, HOXC12 or the HOTAIR lncRNA inclusion. SNP analysis revealed HOXC11 p.Ser191Phe segregating with clubfoot in a small family and enrichment of HOXC12 p.Asn176Lys in patients with clubfoot or vertical talus (rs189468720, p=0.0057, OR=3.8). Defects in limb morphogenesis include shortened and overlapping toes, as well as peroneus muscle hypoplasia. Finally, HOXC and HOXD gene expression is reduced in fibroblasts from a patient with a 5' HOXC deletion, consistent with previous studies demonstrating that dosage of lncRNAs alters expression of HOXD genes in trans.

CONCLUSIONS

Because HOXD10 has been implicated in the aetiology of congenital vertical talus, variation in its expression may contribute to the lower limb phenotypes occurring with 5' HOXC microdeletions. Identification of 5' HOXC microdeletions highlights the importance of transcriptional regulators in the aetiology of severe lower limb malformations and will improve their diagnosis and management.

Familial congenital bilateral vocal fold paralysis: a novel gene translocation

OBJECTIVES

True vocal fold (TVF) paralysis is a common cause of neonatal stridor and airway obstruction, though bilateral TVF paralysis is seen less frequently. Rare cases of familial congenital TVF paralysis have been described with implied genetic origin, but few genetic abnormalities have been discovered to date. The purpose of this study is to describe a novel chromosomal translocation responsible for congenital bilateral TVF immobility.

METHODS

The charts of three patients were retrospectively reviewed: a 35 year-old woman and her two children. The mother had bilateral TVF paralysis at birth requiring tracheotomy. Her oldest child had a similar presentation at birth and also required tracheotomy, while the younger child had laryngomalacia without TVF paralysis. Standard karyotype analysis was done using samples from all three patients and the parents of the mother, to assess whether a chromosomal abnormality was responsible.

RESULTS

Karyotype analysis revealed the same balanced translocation between chromosomes 5 and 14, t(5;14) (p15.3, q11.2) in the mother and her two daughters. No other genetic abnormalities were identified. Neither maternal grandparent had the translocation, which appeared to be a spontaneous mutation in the mother with autosomal dominant inheritance and variable penetrance.

CONCLUSIONS

A novel chromosomal translocation was identified that appears to be responsible for familial congenital bilateral TVF paralysis. While there are other reports of genetic abnormalities responsible for this condition, we believe this is the first describing this particular translocation.

[Clubfoot's prenatal ultrasound diagnosis: is amniocentesis always warranted? About 124 cases]

OBJECTIVES

Analyze factors leading to isolated clubfoot's occurrence, identify clubfeet associated pathologies, and discuss the opportunity of performing an amniocentesis in cases of isolated clubfoot.

PATIENTS AND METHODS

Between January 2007 and December 2011, all patients diagnosed with clubfoot in our prenatal diagnostic center were retrospectively included. We then defined and analyzed idiopathic or isolated talipses equinovarus (ITEV) and clubfeet associated with others morphologic abnormalities or syndromic talipses equinovarus (STEV).

RESULTS

One hundred and twenty-four clubfeet were analyzed. Forty-seven cases of ITEV, for which 34 caryotypes were performed with a normal result. Risk factors of ITEV in our series were male gender (P=0.0017), a family history of clubfoot (P=0.001) and primiparity (P=0.04). Seventy-seven cases of STEV were diagnosed, 14 of which had chromosomal abnormalities, 18 spina bifida and 10 musculo-skeletal abnormalities. Among the 124 cases of clubfeet, 25 were unilateral and 99 were bilateral. Bilateral talipses equinovarus do not constitute a risk factor of STEV (P=0.8).

DISCUSSION AND CONCLUSION

We did not find any chromosomic abnormalities in cases of ITEV. The results of our study could lead to defer systematic amniocentesis in cases of primiparous women diagnosed with an ITEV, with a familial history of clubfoot and a male fetus. A referent echographist in prenatal diagnosis should still perform a systematic morphologic echography.