Mutation screening of genes associated with congenital talipes equinovarus in pakistani families

Whole exome sequencing improves genetic diagnosis of fetal clubfoot

OBJECTIVE

This retrospective study aimed to investigate the value of whole exome sequencing (WES) for clubfoot (CF) fetuses with or without other structural abnormalities and to further explore the genetic causes of fetal CF.

METHODS

this study included 83 singleton pregnancies diagnosed with fetal CF referred to our center between January 2016 and March 2022; cases were divided into two groups: isolated CF and non-isolated CF. After excluding cases with positive karyotyping and chromosomal microarray analysis results, WES was performed for the eligible fetuses and parents. Monogenic variants detected by WES and perinatal outcomes were recorded and evaluated at postnatal follow-up.

RESULTS

overall, clinically significant variations were identified in 12.0% (10/83) of fetuses, and the detection rate was significantly higher in the non-isolated than in the isolated CF group (8/36, 22.2% vs. 2/47, 4.3%, p = 0.031). We additionally detected eight (9.6%) fetuses harboring variants of unknown significance. We identified 11 clinically significant variations correlating with clinical phenotypes in nine genes from ten fetuses, with KLHL40 being the most frequent (n = 2). Furthermore, we observed a significant difference in termination and survival rates between isolated and non-isolated CF cases (27.6 vs. 77.8% and 59.6 vs. 19.4%, p < 0.001 for both).

CONCLUSION

our data indicate that WES has a high additional diagnostic yield for the molecular diagnosis of fetal CF, markedly enhancing existing prenatal diagnostic capabilities and expanding our understanding of intrauterine genetic disorders, thus assisting us to better interpret fetal phenotype in the future.

An intrafamilial phenotypic variability in Ellis-Van Creveld syndrome due to a novel 27 bps deletion mutation

Ellis-van Creveld (EvC) syndrome is an autosomal recessive disease, characterized by ectodermal, skeletal, and cardiac anomalies. We report intrafamilial phenotypic variability in three new EvC syndrome cases. Affected males in this study showed only ectodermal abnormalities, whereas an affected female showed the classical presentation of EvC Syndrome, including bilateral postaxial polydactyly of hands and feet, and congenital heart defects. Whole exome sequencing was performed to identify the causative variant, followed by validation and segregation analysis using Sanger sequencing. A homozygous deletion variant (c.731_757del) was identified in exon 6 of the EVC gene (NM_153717.2). The identified variant is considered to be the most likely candidate variant for the EvC syndrome in the family based on previous reports validating the role of EVC variants in the EvC syndrome. The disease correctly segregated in the family members, as all affected members were homozygous, and obligate carriers were heterozygous. Our family is remarkable in highlighting the variable expressivity of the EvC phenotype within the same family, due to a homozygous deletion mutation in the EVC gene. The variable expressivity might be due to the hypomorphic nature of mutation, or the presence of additional variants in modifier genes or in the regulatory regions of the EVC/EVC2 genes.

Association Between TPM1 Gene Polymorphisms and Idiopathic Congenital Talipes Equinovarus Risk in a Chinese Population

Background: Idiopathic congenital talipes equinovarus (ICTEV) is one of the most common congenital deformities of children, and dysplasia of the striated muscle may be one of the causes of ICTEV. Previous studies have shown that polymorphisms of the rs4075583 SNP in the tropomyosin gene 1 (TPM1) were associated with ICTEV in Caucasian children. However, there are no studies investigating the correlations of TPM gene polymorphisms with the risk of ICTEV in Chinese children. Methods: We conducted a case-control study, including 430 children with ICTEV and 891 ICTEV-free children. We explored the potential correlations of three TPM gene polymorphisms (TPM1/rs4075583 G>A, tropomyosin gene 2 (TPM2)/rs2145925 C>T, and TPM2/rs2025126 G>A) with ICTEV risk. The three single nucleotide polymorphisms (SNPs) were genotyped using a TaqMan method. We calculated the odds ratios (ORs) and adjusted ORs and their 95% confidence intervals (CIs) to explore the associations between these selected SNP polymorphisms and ICTEV. Results: TPM1 rs4075583 A was found to be associated with an increased ICTEV risk (AA vs. GG: adjusted OR = 1.70, 95% CI = 1.15-2.49, p = 0.007; and GG/GA vs. AA: adjusted OR = 1.62, 95% CI = 1.14-2.31, p = 0.0071) after adjusting for age and sex. In addition, a risk effect of rs4075583 GA/AA with ICETV was observed for patients with affected right feet (adjusted OR = 1.62, 95% CI = 1.10-2.39, p = 0.014) in the stratified analysis. However, there were no significant differences in the risk for ICTEV associated with the rs2145925 and rs2025126 polymorphisms. Conclusion: These results indicate that the TPM1 rs4075583 G > A polymorphism is associated with ICTEV risk in a southern Chinese population; however, this finding needs to be confirmed in larger studies and through mechanistic studies.