Genomic organization and chromosomal localization of three members of the UDP-N-acetylgalactosamine: polypeptide N- acetylgalactosaminyltransferase family

A homologous family of UDP- N -acetylgalactosamine: polypeptide N - acetylgalactosaminyltransferases (GalNAc-transferases) initiate O- glycosylation. These transferases share overall amino acid sequence similarities of approximately 45-50%, but segments with higher similarities of approximately 80% are found in the putative catalytic domain. Here we have characterized the genomic organization of the coding regions of three GalNAc-transferase genes and determined their chromosomal localization. The coding regions of GALNT1 , -T2 , and -T3 were found to span 11, 16, and 10 exons, respectively. Several intron/exon boundaries were conserved within the three genes. One conserved boundary was shared in a homologous C. elegans GalNAc- transferase gene. Fluorescence in situ hybridization showed that GALNT1 , -T2 , and -T3 are localized at chromosomes 18q12-q21, 1q41-q42, and 2q24-q31, respectively. These results suggest that the members of the polypeptide GalNAc-transferase family diverged early in evolution from a common ancestral gene through gene duplication.      

Transport of (Glyco)Sphingolipids in and Between Cellular Membranes; Multidrug Transporters and Lateral Domains

Sphingolipids are highly enriched in the outer leaflet of the plasma membrane lipid bilayer. However, the first glycolipid, glucosylceramide, is synthesized in the opposite, cytosolic leaflet of the Golgi membrane. This has led us to experiments which suggest that the level of glucosylceramide in the cytosolic surface is carefully regulated both by the balance between synthesis and hydrolysis and by transport away from this surface through translocators, multidrug transporters, the same molecules that make cancer cells resistant to chemotherapy. Our data suggest a role for newly synthesized glucosylceramide not only in the formation of domains in the luminal leaflet of the Golgi but also on the cytosolic surface of this organelle.     

Glucosylceramide modulates membrane traffic along the endocytic pathway

Glycosphingolipids are endocytosed and targeted to the Golgi apparatus, but are mistargeted to lysosomes in numerous sphingolipidoses. Substrate reduction therapy utilizes imino sugars to inhibit glucosylceramide synthase and potentially abrogate the effects of storage. Gaucher disease is a hereditary deficiency in glucocerebrosidase leading to glucosylceramide accumulation; however, Gaucher fibroblasts exhibited normal Golgi transport of lactosylceramide. To better understand the effects of glycosphingolipid accumulation on intracellular trafficking and the use of imino sugar inhibitors, we studied sphingolipid endocytosis in fibroblast and macrophage models for Gaucher disease. Treatment of fibroblasts or RAW macrophages with conduritol B epoxide, an inhibitor of lysosomal glucocerebrosidase, resulted in a change in the endocytic targeting of lactosylceramide from the Golgi to the lysosomes. Co-treatment of macrophages with conduritol B-epoxide and 12-25 microM N-butyldeoxygalactonojirimycin, an inhibitor of glycosphingolipid biosynthesis, prevented the mistargeting of lactosylceramide to the lysosomes and restored trafficking to the Golgi. Surprisingly, higher doses (>25 microM) of NB-DGJ induced targeting of lactosylceramide to the lysosomes, even in the absence of conduritol B-epoxide. These data demonstrate that both increases and decreases in glucosylceramide levels can dramatically alter the endocytic targeting of lactosylceramide and suggest a role for glucosylceramide in regulation of membrane transport.     

alpha-L-iduronidase premature stop codons and potential read-through in mucopolysaccharidosis type I patients

alpha-L-Iduronidase is a glycosyl hydrolase involved in the sequential degradation of the glycosaminoglycans heparan sulphate and dermatan sulphate. A deficiency in alpha-L-iduronidase results in the lysosomal accumulation and urinary secretion of partially degraded glycosaminoglycans and is the cause of the lysosomal storage disorder mucopolysaccharidosis type I (MPS I; Hurler and Scheie syndromes; McKusick 25280). The premature stop codons Q70X and W402X are two of the most common alpha-l-iduronidase gene (IDUA) mutations accounting for up to 70% of MPS I disease alleles in some populations. Here, we have reported a new mutation, making a total of 15 different mutations that can cause premature IDUA stop codons and have investigated the biochemistry of these mutations. Natural stop codon read-through was dependent on the fidelity of the codon when evaluated at Q70X and W402X in CHO-K1 cells, but the three possible stop codons TAA, TAG and TGA, had different effects on mRNA stability and this effect was context dependent. In CHO-K1 cells expressing the Q70X and W402X mutations, the level of gentamicin-enhanced stop codon read-through was slightly less than the increment in activity caused by a lower fidelity stop codon. In this system, gentamicin had more effect on read-through for the TAA and TGA stop codons when compared to the TAG stop codon. In an MPS I patient study, premature TGA stop codons were associated with a slightly attenuated clinical phenotype, when compared to classical Hurler syndrome (e.g. W402X/W402X and Q70X/Q70X genotypes with TAG stop codons). Natural read-through of premature stop codons is a potential explanation for variable clinical phenotype in MPS I patients. Enhanced stop codon read-through is a potential treatment strategy for a large sub-group of MPS I patients.     

1895-1950年间的中国体质人类学研究与教学活动述略

1895-1950年间的中国体质人类学活动,既注重研究和教学相结合,又注重体质调查和文化调查相结合,生物与考古并重,其研究目的在于揭示各族群的体质差异,以及人类的演化问题.先期主要由外国学者进入并开展研究和教学活动,后期则主要由中国本土人类学家推动这一工作.另外,此一阶段后期体质人类学发展深受中日战争影响,战争前主要分布于北方、华东和华南,战争爆发期间主要集中于西南,战争后则主要集中于东南和华南.     

Mutations in the TGFβ binding-protein-like domain 5 of FBN1 are responsible for acromicric and geleophysic dysplasias

Geleophysic (GD) and acromicric dysplasia (AD) belong to the acromelic dysplasia group and are both characterized by severe short stature, short extremities, and stiff joints. Although AD has an unknown molecular basis, we have previously identified ADAMTSL2 mutations in a subset of GD patients. After exome sequencing in GD and AD cases, we selected fibrillin 1 (FBN1) as a candidate gene, even though mutations in this gene have been described in Marfan syndrome, which is characterized by tall stature and arachnodactyly. We identified 16 heterozygous FBN1 mutations that are all located in exons 41 and 42 and encode TGFβ-binding protein-like domain 5 (TB5) of FBN1 in 29 GD and AD cases. Microfibrillar network disorganization and enhanced TGFβ signaling were consistent features in GD and AD fibroblasts. Importantly, a direct interaction between ADAMTSL2 and FBN1 was demonstrated, suggesting a disruption of this interaction as the underlying mechanism of GD and AD phenotypes. Although enhanced TGFβ signaling caused by FBN1 mutations can trigger either Marfan syndrome or GD and AD, our findings support the fact that TB5 mutations in FBN1 are responsible for short stature phenotypes.     

How does farmer connectivity influence livestock genetic structure? A case‐study in a Vietnamese goat population

Assessing how genes flow across populations is a key component of conservation genetics. Gene flow in a natural population depends on ecological traits and the local environment, whereas for a livestock population, gene flow is driven by human activities. Spatial organization, relationships between farmers and their husbandry practices will define the farmer's network and so determine farmer connectivity. It is thus assumed that farmer connectivity will affect the genetic structure of their livestock. To test this hypothesis, goats reared by four different ethnic groups in a Vietnamese province were genotyped using 16 microsatellites. A Bayesian approach and spatial multivariate analysis (spatial principal component analysis, sPCA) were used to identify subpopulations and spatial organization. Ethnic group frequencies, husbandry practices and altitude were used to create cost maps that were implemented in a least-cost path approach. Genetic diversity in the Vietnamese goat population was low (0.508) compared to other local Asian breeds. Using a Bayesian approach, three clusters were identified. sPCA confirmed these three clusters and also that the genetic structure showed a significant spatial pattern. The least-cost path analysis showed that genetic differentiation was significantly correlated (0.131–0.207) to ethnic frequencies and husbandry practices. In brief, the spatial pattern observed in the goat population was the result of complex gene flow governed by the spatial distribution of ethnic groups, ethnicity and husbandry practices. In this study, we clearly linked the livestock genetic pattern to farmer connectivity and showed the importance of taking into account spatial information in genetic studies.