Deletion of Cdc42 in embryonic cardiomyocytes results in right ventricle hypoplasia

Ultrasound Phenotype, Genetic Analysis, and Pregnancy Outcomes of Fetuses With 1p36 Deletion Syndrome

BACKGROUND

The intrauterine ultrasound phenotype, genotype, pregnancy outcome, and neonatal prognosis of fetuses with 1p36 deletion syndrome were retrospectively analyzed, as previous reports are limited.

METHODS

Pregnant women (25,000) who underwent interventional prenatal diagnosis between December 2016 and March 2024 were selected. Fetal villus tissue, amniotic fluid, or umbilical cord blood were extracted for single nucleotide polymorphism array (SNP-array) detection under ultrasound guidance.

RESULTS

Thirteen fetuses had 1p36 deletions involving fragments that were 0.46-22.5 Mb. Six and seven fetuses had large and small copy number variation (CNV) fragment deletions in the 1p36 region, respectively. Two fetuses had normal ultrasound phenotypes, three underwent early spontaneous abortion, one had isolated ventricular septal defect, one had isolated mild ventriculomegaly, two had mild ventriculomegaly associated with increased renal echogenicity, one had mild ventriculomegaly associated with ventricular septal defect, one had severe ventriculomegaly associated with ventricular septal defect and fetal growth restriction, one had tricuspid valve dysplasia, and one had nasal bone dysplasia. Three 1p36 deletions were de novo, and one was paternally inherited. There were three cases of early spontaneous abortion, seven terminations, and three routine postnatal follow-ups.

CONCLUSIONS

High-resolution SNP-arrays are suitable for the prenatal diagnosis of 1p36 deletion syndrome.

Vasorin deficiency leads to cardiac hypertrophy by targeting MYL7 in young mice

Vasorin (VASN) is an important transmembrane protein associated with development and disease. However, it is not clear whether the death of mice with VASN deficiency (VASN^-/- ) is related to cardiac dysfunction. The aim of this research was to ascertain whether VASN induces pathological cardiac hypertrophy by targeting myosin light chain 7 (MYL7). VASN^-/- mice were produced by CRISPR/Cas9 technology and inbreeding. PCR amplification, electrophoresis, real-time PCR and Western blotting were used to confirm VASN deficiency. Cardiac hypertrophy was examined by blood tests, histological analysis and real-time PCR, and key downstream factors were identified by RNA sequencing and real-time PCR. Western blotting, immunohistochemistry and electron microscopy analysis were used to confirm the downregulation of MYL7 production and cardiac structural changes. Our results showed that sudden death of VASN^-/- mice occurred 21-28 days after birth. The obvious increases in cardiovascular risk, heart weight and myocardial volume and the upregulation of hypertrophy marker gene expression indicated that cardiac hypertrophy may be the cause of death in young VASN^-/- mice. Transcriptome analysis revealed that VASN deficiency led to MYL7 downregulation, which induced myocardial structure abnormalities and disorders. Our results revealed a pathological phenomenon in which VASN deficiency may lead to cardiac hypertrophy by downregulating MYL7 production. However, more research is necessary to elucidate the underlying mechanism.

In vivo Functional Genomics for Undiagnosed Patients: The Impact of Small GTPases Signaling Dysregulation at Pan-Embryo Developmental Scale

While individually rare, disorders affecting development collectively represent a substantial clinical, psychological, and socioeconomic burden to patients, families, and society. Insights into the molecular mechanisms underlying these disorders are required to speed up diagnosis, improve counseling, and optimize management toward targeted therapies. Genome sequencing is now unveiling previously unexplored genetic variations in undiagnosed patients, which require functional validation and mechanistic understanding, particularly when dealing with novel nosologic entities. Functional perturbations of key regulators acting on signals' intersections of evolutionarily conserved pathways in these pathological conditions hinder the fine balance between various developmental inputs governing morphogenesis and homeostasis. However, the distinct mechanisms by which these hubs orchestrate pathways to ensure the developmental coordinates are poorly understood. Integrative functional genomics implementing quantitative in vivo models of embryogenesis with subcellular precision in whole organisms contribute to answering these questions. Here, we review the current knowledge on genes and mechanisms critically involved in developmental syndromes and pediatric cancers, revealed by genomic sequencing and in vivo models such as insects, worms and fish. We focus on the monomeric GTPases of the RAS superfamily and their influence on crucial developmental signals and processes. We next discuss the effectiveness of exponentially growing functional assays employing tractable models to identify regulatory crossroads. Unprecedented sophistications are now possible in zebrafish, i.e., genome editing with single-nucleotide precision, nanoimaging, highly resolved recording of multiple small molecules activity, and simultaneous monitoring of brain circuits and complex behavioral response. These assets permit accurate real-time reporting of dynamic small GTPases-controlled processes in entire organisms, owning the potential to tackle rare disease mechanisms.

Systems Analysis Implicates WAVE2 Complex in the Pathogenesis of Developmental Left-Sided Obstructive Heart Defects

Genetic variants are the primary driver of congenital heart disease (CHD) pathogenesis. However, our ability to identify causative variants is limited. To identify causal CHD genes that are associated with specific molecular functions, the study used prior knowledge to filter de novo variants from 2,881 probands with sporadic severe CHD. This approach enabled the authors to identify an association between left ventricular outflow tract obstruction lesions and genes associated with the WAVE2 complex and regulation of small GTPase-mediated signal transduction. Using CRISPR zebrafish knockdowns, the study confirmed that WAVE2 complex proteins brk1, nckap1, and wasf2 and the regulators of small GTPase signaling cul3a and racgap1 are critical to cardiac development.

Efficient Mining of Variants From Trios for Ventricular Septal Defect Association Study

Ventricular septal defect (VSD) is a fatal congenital heart disease showing severe consequence in affected infants. Early diagnosis plays an important role, particularly through genetic variants. Existing panel-based approaches of variants mining suffer from shortage of large panels, costly sequencing, and missing rare variants. Although a trio-based method alleviates these limitations to some extent, it is agnostic to novel mutations and computational intensive. Considering these limitations, we are studying a novel variants mining algorithm from trio-based sequencing data and apply it on a VSD trio to identify associated mutations. Our approach starts with irrelevant k-mer filtering from sequences of a trio via a newly conceived coupled Bloom Filter, then corrects sequencing errors by using a statistical approach and extends kept k-mers into long sequences. These extended sequences are used as input for variants needed. Later, the obtained variants are comprehensively analyzed against existing databases to mine VSD-related mutations. Experiments show that our trio-based algorithm narrows down candidate coding genes and lncRNAs by about 10- and 5-folds comparing with single sequence-based approaches, respectively. Meanwhile, our algorithm is 10 times faster and 2 magnitudes memory-frugal compared with existing state-of-the-art approach. By applying our approach to a VSD trio, we fish out an unreported gene—CD80, a combination of two genes—MYBPC3 and TRDN and a lncRNA—NONHSAT096266.2, which are highly likely to be VSD-related.

A de novo Mutation in the MTUS1 Gene Decreases the Risk of Non-compaction of Ventricular Myocardium via the Rac1/Cdc42 Pathway

Background: The MTUS1 gene encodes a microtubule-associated protein involved in multiple processes including cell polarity and microtubule balance during myocardial development. Aims: To investigate the association between a de novo c. 2617A->C mutation in MTUS1 (NM_001001924.2) and non-compaction of ventricular myocardium (NVM) and explore the potential mechanisms. Methods: A de novo mutation in MTUS1 was identified for a familial pedigree with NVM. Lentiviral vectors containing MTUS1 wild type or the mutation MTUS1 were constructed and co-infected into HEK-293 cells. MTUS1, Rac1/Cdc42, α-tubulin, α/β-tubulin, polarity protein (PAR6), and the morphology of daughter cells were measured by real-time PCR, Western blot, and immunofluorescence assays, respectively. Results: The lentiviral vectors were constructed successfully. Immunofluorescence assays revealed the fluorescence intensity of α-tubulin to be decreased and α/β-tubulin to be increased in the mutation MTUS1 group. The fluorescence intensity of PAR6 was higher and morphology of the daughter cells in the mutation group was different from the wild type group. The phosphorylation of Rac1/Cdc42 in the mutation group was significantly lower than in the wild type group. Conclusions: A de novo mutation in MTUS1 decreased the stability of microtubules and increased cell polarity via the Rac1/Cdc42 pathway, which may partly elucidate the mechanism underlying cellular protection in NVM.