The human ASM (adult skeletal muscle) gene: expression and chromosomal assignment to 11p15

A rat adult skeletal muscle probe (Asm15) originated from a rhabdomyosarcoma was used to isolate the human homologous sequence from a placenta cDNA library. Among several positive clones the longest EcoRI-EcoRI insert (ASM1) obtained was 1875 bp long with 72% homology with rat Asm15 cDNA sequence. Important variations of ASM1 RNA level were observed in different adult skeletal muscles. Expression of a 29kD ASM1 protein was demonstrated in human adult skeletal muscle lysates using an antiserum (PB1579) raised against the C terminal region of the rat Asm15 protein. The human ASM gene was assigned by somatic cell analysis with human (ASM1) and rat (Asm15) probes to chromosome 11, and by in situ hybridization with the human probe to 11p15, a chromosome region involved in human embryonal rhabdomyosarcomas. Except for the presence of a HindII restriction site, the results obtained for the restriction map and the sequence of ASM1 cDNA (data not shown) exhibited extensive homology with the human H19 DNA sequence which have been mapped with a mouse probe also in 11p15. This suggests that ASM/Asm and H19 may represent the same sequence (in this hypothesis the presence of the supplementary HindII site in our ASM1 probe is explained by polymorphic variability). However it was reported that human and mouse H19 mRNA did not encode for a protein but acted as an RNA molecule whereas in our present study ASM protein was detected in human adult skeletal muscle. This could be explained by important regulation of ASM protein expression during development and cell differentiation. However we cannot exclude for the different species studied (mouse, rat, and man) the hypothesis that H19 and ASM/Asm mRNA may represent two distinct messengers from the same gene or even from duplicated genes.     

c-myc oncogene expression inhibits the initiation of myogenic differentiation

The role of c-myc oncogene expression in myogenic differentiation has been established by transfecting rat myoblasts of the L6 cell line with plasmid pMT-myc, in which the c-myc coding sequences were under the control of the metallothionein I promoter. We observed that the constitutive expression of the exogenous c-myc gene inhibits muscular differentiation. A diminution of the endogenous c-myc gene expression occurs within the first 24 h after the transfer of the cells to a differentiating medium. This early decrease of c-myc expression is required for cell differentiation to occur. We have also observed that exogenous myc gene expression has no effect on endogenous myc expression.     

Telomeres and P-element of Drosophila melanogaster contain sequences that replicate autonomously in Saccharomyces cerevisiae

Summary We have isolated restriction fragments from a shotgun collection of Drosophila DNA which function as autonomously replicating sequences (ARS) in Saccharomyces cerevisiae and hybridize with telomeric regions of the 2L, 2R, 4, and X chromosomes. In an independently obtained set of D. melanogaster clones five fragments hybridize in situ with telomeres and a number of internal sites. Two of them also contain ARSs. A Drosophila mobile P-element also possesses ARS activity in yeast.     

Changes in the frequency and diversity of messenger RNA populations in the course of myogenic differentiation.

Complementary DNAs (cDNAs) were synthesized from polyadenylated RNAs of myoblasts and myotubes and used to analyze changes in the sequence complexity and frequency distribution of messenger RNAs during myogenesis in vitro. cDNA . polyadenylated-RNA hybridization kinetics show the presence of messenger RNA sequences specific for myotubes in fully differentiated muscle cultures. These sequences are accumulated just prior to fusion, as was shown by hybridizations of myotube cDNA and total cytoplasmic RNAs from cells at different stages of differentiation. The myotube cDNA can be enriched 10-fold in myotube-specific RNA species by a hybridization with cytoplasmic RNAs from myoblasts and subsequent removal of these hybridized sequences by hydroxyapatite.     

Influence of deficiency of the histone gene-containing 38B-40 region on X-chromosome template activity and the white gene position effect variegation in Drosophila melanogaster.

Summary The deficiency of the 38B-40 region containing histone genes in one of the 2nd chromosomes of D. melanogaster triploid intersexes increases the template activity of X-chromosomes both in vivo and in vitro without noticeably affecting autosome activity. This deficiency in the heterozygous state inhibits the variegated position effect of the white gene in the T(1;3)w ^vcotranslocation in diploid females and males, but not affect their rate of development. The variegation suppressor Su(var)hg-1 not only suppress the gene position effect in diploid flies, but also increases the template activity of X-chromosomes in triploid intersexes.The results are discussed with respect to the dependence of gene activity on the structure of chromosomes (density of DNP packing).     

中国西北沙漠夜间活动的东鳖甲属昆虫二新种(鞘翅目:拟步甲科:漠甲亚科)

记述中国西北地区东鳖甲属2新种:巴丹东鳖甲A.badainica Ba,Ren&Liu sp.nov.和古尔班东鳖甲A.gurbantunggutica Ba&Ren sp.nov.,提供了主要鉴别特征和形态图,并简要讨论了其昼夜活动规律.