Differential role of CENP-A in the segregation of holocentric C. elegans chromosomes during meiosis and mitosis

Two distinct chromosome architectures are prevalent among eukaryotes: monocentric, in which localized centromeres restrict kinetochore assembly to a single chromosomal site, and holocentric, in which diffuse kinetochores form along the entire chromosome length. During mitosis, both chromosome types use specialized chromatin, containing the histone H3 variant CENP-A, to direct kinetochore assembly. For the segregation of recombined homologous chromosomes during meiosis, monocentricity is thought to be crucial for limiting spindle-based forces to one side of a crossover and to prevent recombined chromatids from being simultaneously pulled towards both spindle poles. The mechanisms that allow holocentric chromosomes to avert this fate remain uncharacterized. Here, we show that markedly different mechanisms segregate holocentric chromosomes during meiosis and mitosis in the nematode Caenorhabditis elegans. Immediately prior to oocyte meiotic segregation, outer-kinetochore proteins were recruited to cup-like structures on the chromosome surface via a mechanism that is independent of CENP-A. In striking contrast to mitosis, both oocyte meiotic divisions proceeded normally following depletion of either CENP-A or the closely associated centromeric protein CENP-C. These findings highlight a pronounced difference between the segregation of holocentric chromosomes during meiosis and mitosis and demonstrate the potential to uncouple assembly of outer-kinetochore proteins from CENP-A chromatin.     

Prevalence of ultrasonography proved polycystic ovaries in North Indian women with type 2 diabetes mellitus

Background  

Polycystic ovaries (PCO) and their clinical expression (the polycystic ovary syndrome [PCOS]) as well as type 2 diabetes mellitus (T2DM) are common medical conditions linked through insulin resistance. We studied the prevalence of PCO and PCOS in women with diet and/or oral hypoglycemic treated T2DM and non-diabetic control women.     

Analysis of microtubule polymerization in vitro and during the cell cycle in Xenopus egg extracts

Microtubules are dynamic polymers that participate in multiple cellular processes such as vesicular transport and cell division. Microtubule dynamics alter dramatically during the cell cycle. An excellent system to study microtubule dynamics is Xenopus egg extracts since it is a system that is open to manipulation. The extracts can be cycled between mitosis and interphase allowing the study of microtubules in these phases as well as during cell cycle transitions. Here, we provide simple assays to study microtubules in extracts and in vitro using purified components. Protocols are provided for the purification of frog tubulin, microtubule pelleting from extracts and in vitro, assembly of microtubule structures in extracts, and isolation of microtubule-associated proteins from extract. These methods can be used to analyze the effect of a protein of interest on the microtubule cytoskeleton.     

A novel autosomal recessive non-syndromic hearing impairment locus (DFNB47) maps to chromosome 2p25.1-p24.3

Hereditary hearing impairment (HI) displays extensive genetic heterogeneity. Autosomal recessive (AR) forms of prelingual HI account for ~75% of cases with a genetic etiology. A novel AR non-syndromic HI locus (DFNB47) was mapped to chromosome 2p25.1-p24.3, in two distantly related Pakistani kindreds. Genome scan and fine mapping were carried out using microsatellite markers. Multipoint linkage analysis resulted in a maximum LOD score of 4.7 at markers D2S1400 and D2S262. The three-unit support interval was bounded by D2S330 and D2S131. The region of homozygosity was found within the three-unit support interval and flanked by markers D2S2952 and D2S131, which corresponds to 13.2 cM according to the Rutgers combined linkage-physical map. This region contains 5.3 Mb according to the sequence-based physical map. Three candidate genes, KCNF1, ID2 and ATP6V1C2 were sequenced, and were found to be negative for functional sequence variants.     

Detection of common mutations in the GALT gene through ARMS

Type I galactosemia is an inborn error resulting from mutations on both alleles of the GALT gene, which leads to the absence or deficiency of galactose-1-phosphate uridyltranseferase (GALT), the second of three enzymes catalyzing the conversion of galactose into glucose. On the basis of residual GALT activity, Type I galactosemia is classified into severe “Classical” and mild “Duarte” phenotypes. Classical galactosemia is frequently associated with S135L, Q188R and K285N mutations in the GALT gene. The functionally neutral N314D variation in the GALT gene is associated with Duarte galactosemia and is widespread among various worldwide populations. The present study aimed at detecting S135L, Q188R and K285N mutations and the N314D variant in the GALT gene by PCR using amplification refractory mutation system (ARMS). ARMS assays were established using standard DNA samples and were used for 8 galactosemia patients and 190 unrelated normal subjects all of Pakistani origin. S135L and K285N mutations were present neither in galactosemia patients nor in normal subjects. Only one galactosemia patient carried Q188R mutation that was in homozygous state. However, the N314D variant was frequently found both in affected (7 out of 16 alleles) and normal subjects (55 out of 380 alleles). This finding indicates that Duarte allele D314 might be far more common in Pakistani population than in European and North American ones.     

Interplay of filaggrin loss-of-function variants, allergic sensitization, and eczema in a longitudinal study covering infancy to 18 years of age

Background

Immune specific genes as well as genes regulating the formation of skin barrier are major determinants for eczema manifestation. There is a debate as to whether allergic sensitization and filaggrin gene (FLG) variants lead to eczema or FLG variants and eczema increase the risk of allergic sensitization. To investigate the time-order between eczema and allergic sensitization with respect to FLG variants, data from a large prospective study covering infancy to late adolescence were analyzed.

Methodology/Principal Findings

Repeated measurements of eczema and allergic sensitization (documented by skin prick tests) at ages 1, 2, 4, 10, and 18 years were ascertained in the Isle of Wight birth cohort (n = 1,456). Three transition periods were analyzed: age 1-or-2 to 4, 4 to 10, and 10 to 18 years. FLG variants were genotyped in 1,150 participants. Over the three transition periods, in temporal sequence analyses of initially eczema-free participants, the combined effect of FLG variants and allergic sensitization showed a 2.92-fold (95% CI: 1.47–5.77) increased risk ratio (RR) of eczema in subsequent examinations. This overall risk was more pronounced at a younger age (transition period 1-or-2 to 4, RR = 6.47, 95% CI: 1.96–21.33). In contrast, FLG variants in combination with eczema showed a weaker, but significant, risk ratio for subsequent allergic sensitization only up to 10 years of age.

Conclusions/Significance

Taking the time order into account, this prospective study demonstrates for the first time, that a combination of FLG variants and allergic sensitization increased the risk of eczema in subsequent years. Also FLG variants interacted with eczema and increased the risk of subsequent allergic sensitization, which, was limited to the younger age. Hence, early restoration of defective skin barrier could prevent allergic sensitization and subsequently reduce the risk of eczema development.