Normal histone modifications on the inactive X chromosome in ICF and Rett syndrome cells: implications for methyl-CpG binding proteins

BACKGROUND: In mammals, there is evidence suggesting that methyl-CpG binding proteins may play a significant role in histone modification through their association with modification complexes that can deacetylate and/or methylate nucleosomes in the proximity of methylated DNA. We examined this idea for the X chromosome by studying histone modifications on the X chromosome in normal cells and in cells from patients with ICF syndrome (Immune deficiency, Centromeric region instability, and Facial anomalies syndrome). In normal cells the inactive X has characteristic silencing type histone modification patterns and the CpG islands of genes subject to X inactivation are hypermethylated. In ICF cells, however, genes subject to X inactivation are hypomethylated on the inactive X due to mutations in the DNA methyltransferase (DNMT3B) genes. Therefore, if DNA methylation is upstream of histone modification, the histones on the inactive X in ICF cells should not be modified to a silent form. In addition, we determined whether a specific methyl-CpG binding protein, MeCP2, is necessary for the inactive X histone modification pattern by studying Rett syndrome cells which are deficient in MeCP2 function. RESULTS: We show here that the inactive X in ICF cells, which appears to be hypomethylated at all CpG islands, exhibits normal histone modification patterns. In addition, in Rett cells with no functional MeCP2 methyl-CpG binding protein, the inactive X also exhibits normal histone modification patterns. CONCLUSIONS: These data suggest that DNA methylation and the associated methyl-DNA binding proteins may not play a critical role in determining histone modification patterns on the mammalian inactive X chromosome at the sites analyzed

Abnormal X : autosome ratio, but normal X chromosome inactivation in human triploid cultures

BACKGROUND: X chromosome inactivation (XCI) is that aspect of mammalian dosage compensation that brings about equivalence of X-linked gene expression between females and males by inactivating one of the two X chromosomes (Xi) in normal female cells, leaving them with a single active X (Xa) as in male cells. In cells with more than two X's, but a diploid autosomal complement, all X's but one, Xa, are inactivated. This phenomenon is commonly thought to suggest 1) that normal development requires a ratio of one Xa per diploid autosomal set, and 2) that an early event in XCI is the marking of one X to be active, with remaining X's becoming inactivated by default. RESULTS: Triploids provide a test of these ideas because the ratio of one Xa per diploid autosomal set cannot be achieved, yet this abnormal ratio should not necessarily affect the one-Xa choice mechanism for XCI. Previous studies of XCI patterns in murine triploids support the single-Xa model, but human triploids mostly have two-Xa cells, whether they are XXX or XXY. The XCI patterns we observe in fibroblast cultures from different XXX human triploids suggest that the two-Xa pattern of XCI is selected for, and may have resulted from rare segregation errors or Xi reactivation. CONCLUSION: The initial X inactivation pattern in human triploids, therefore, is likely to resemble the pattern that predominates in murine triploids, i.e., a single Xa, with the remaining X's inactive. Furthermore, our studies of XIST RNA accumulation and promoter methylation suggest that the basic features of XCI are normal in triploids despite the abnormal X:autosome ratio

Use of a novel bluetooth-connected device to measure handgrip strength: A practical tool to help healthcare professionals identify adults at nutritional risk

Summary: Background and Aims: Low muscle strength is strongly tied to poor nutrition status, and nutritional interventions are likewise linked to maintenance and restoration of muscle strength and functional status. Nutrition plays a vital role in muscle mass, strength, and function, and losses in muscle (strength, function, and mass) are associated with poor health outcomes and added costs for healthcare services. For this study of outpatients, the main objective was to identify those at risk for low muscle strength, as evidenced by low handgrip strength (HGS) measures with risk stratified by age and sex. Methods: This was a two-part study on HGS measures in adults attending outpatient clinics in India. In part one, we conducted HGS tests on dominant and non-dominant hands of patients who qualified for the study. For HGS measures, we used a validated tool, the SQUEGG device, a smart handgrip trainer, along with its companion Bluetooth-connected app, the Muscle Strength Assessment Tool (MSAT) app. In part two, we collected Healthcare Practitioners' (HCPs) feedback via a short digital survey on the use of the SQUEGG device + the MSAT app to do HGS risk screening as an indicator of needed nutritional intervention. Results: Nearly a third of community-living adults in India exhibited low HGS among the 3036 sampled. At each age stratum, dominant-hand HGS in women was lower by 25%–35% compared to men. Among 353 HCPs, 293 (83%) provided insights via survey, and 85% of surveyed HCPs (n = 249) strongly agreed or agreed that the SQUEGG device + MSAT app helped them identify HGS issues among their patients, and 85% (n = 248) agreed or strongly agreed they would like to continue using the SQUEGG device + MSAT app to inform their practice. Nearly all surveyed HCPs (98%, n = 288) recommended an oral nutritional supplement (ONS) to their patients with identified low HGS. Conclusions: Our findings demonstrate that HCPs would like to continue use of the SQUEGG device + MSAT app as it helped them identify adult patients who had decreased HGS (about 30% of the study population), in turn identifying opportunities to use nutritional interventions such as ONS to address nutrition shortfalls and to restore functional status

Abnormal X : autosome ratio, but normal X chromosome inactivation in human triploid cultures

Abstract Background X chromosome inactivation (XCI) is that aspect of mammalian dosage compensation that brings about equivalence of X-linked gene expression between females and males by inactivating one of the two X chromosomes (Xi) in normal female cells, leaving them with a single active X (Xa) as in male cells. In cells with more than two X's, but a diploid autosomal complement, all X's but one, Xa, are inactivated. This phenomenon is commonly thought to suggest 1) that normal development requires a ratio of one Xa per diploid autosomal set, and 2) that an early event in XCI is the marking of one X to be active, with remaining X's becoming inactivated by default. Results Triploids provide a test of these ideas because the ratio of one Xa per diploid autosomal set cannot be achieved, yet this abnormal ratio should not necessarily affect the one-Xa choice mechanism for XCI. Previous studies of XCI patterns in murine triploids support the single-Xa model, but human triploids mostly have two-Xa cells, whether they are XXX or XXY. The XCI patterns we observe in fibroblast cultures from different XXX human triploids suggest that the two-Xa pattern of XCI is selected for, and may have resulted from rare segregation errors or Xi reactivation. Conclusion The initial X inactivation pattern in human triploids, therefore, is likely to resemble the pattern that predominates in murine triploids, i.e., a single Xa, with the remaining X's inactive. Furthermore, our studies of XIST RNA accumulation and promoter methylation suggest that the basic features of XCI are normal in triploids despite the abnormal X:autosome ratio.</p