Lower concentrations of folate and vitamin B12 are related to the increased risk of NTDs. Both folate and vitamin B12 intake insufficiency could contribute to the increased risk of NTDs. A dietary supplement, combining folate and vitamin B12, might be an effective measure to decrease the NTDs incidence in Tunisia.
Hypertrophic cardiomyopathy (HCM) is characterized by thickening of the ventricular muscle without dilation and is often associated with dominant pathogenic variants in cardiac sarcomeric protein genes. Here, we report a family with two infants diagnosed with infantileonset HCM and mitral valve dysplasia that led to death before one year of age. Using exome sequencing, we discovered that one of the affected children had a homozygous frameshift variant in Myosin light chain 2 (MYL2:NM_000432.3:c.431_432delCT: p.Pro144Argfs*57; MYL2-fs), which alters the last 20 amino acids of the protein and is predicted to impact the most C-terminal of the three EF-hand domains in MYL2. The parents are unaffected heterozygous carriers of the variant and the variant is absent in control cohorts from gnomAD. The absence of the phenotype in carriers and the infantile presentation of severe HCM is in contrast to HCM associated with dominant MYL2 variants. Immunohistochemical analysis of the ventricular muscle of the deceased patient with the MYL2-fs variant showed a marked reduction of MYL2 expression compared to an unaffected control. In vitro overexpression studies further indicate that the MYL2-fs variant is actively degraded. In contrast, an HCMassociated missense variant (MYL2:p.Gly162Arg) and three other MYL2 stop-gain variants (p.E22*, p.K62*, p.E97*) that result in loss of the EF domains are stably expressed but show impaired localization. The degradation of the MYL2-fs can be rescued by inhibiting the cell's proteasome function supporting a post-translational effect of the variant. In vivo rescue experiments with a Drosophila MYL2-homolog (Mlc2) knockdown model indicate that neither the MYL2-fs nor the MYL2:p.Gly162Arg variant supports normal cardiac function. The tools that we have generated provide a rapid screening platform for functional assessment PLOS GENETICS
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