title: Characterization of msim, a murine homologue of the Drosophila sim transcription factor.
abstract: Mutations in the Drosophila single-minded (sim) gene result in loss of precursor cells that give rise to midline cells of the embryonic central nervous system. During the course of an exon-trapping strategy aimed at identifying transcripts that contribute to the etiology and pathophysiology of Down syndrome, we identified a human exon from the Down syndrome critical region showing significant homology to the Drosophila sim gene. Using a cross-hybridization approach, we have isolated a murine homolog of the Drosophila sim gene, which we designated msim. Nucleotide and predicted amino acid sequence analyses of msim cDNA clones indicate that this gene encodes a member of the basic-helix-loop-helix class of transcription factors. The murine and Drosophila proteins share 88% residues within the basic-helix-loop-helix domain, with an overall homology of 92%. In addition, the N-terminal domain of MSIM contains two PAS dimerization motifs also featured in the Drosophila sim gene product, as well as a small number of other transcription factors. Northern blot analysis of adult murine tissues revealed that the msim gene produces a single mRNA species of approximately 4 kb expressed in a small number of tissues, with the highest levels in the kidneys and lower levels present in skeletal muscle, lung, testis, brain, and heart. In situ hybridization experiments demonstrate that msim is also expressed in early fetal development in the central nervous system and in cartilage primordia. The characteristics of the msim gene are consistent with its putative function as a transcriptional regulator.
authors.affiliation: Department of Biochemistry, McGill University, 3655 Drummond Street, Montreal, Quebec, H3G 1Y6, Canada.
authors.forename: P
authors.initials: P
authors.lastname: Moffett
authors.forename: M
authors.initials: M
authors.lastname: Dayo
authors.forename: M
authors.initials: M
authors.lastname: Reece
authors.forename: M K
authors.initials: MK
authors.lastname: McCormick
authors.forename: J
authors.initials: J
authors.lastname: Pelletier
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D051792:Basic Helix-Loop-Helix Proteins; D016386:Chromosome Walking; D004268:DNA-Binding Proteins / Q000096:biosynthesis / Q000235:genetics*; D004195:Disease Models, Animal; D004314:Down Syndrome / Q000235:genetics; D029721:Drosophila Proteins; D004331:Drosophila melanogaster / Q000235:genetics*; D005314:Embryonic and Fetal Development; D005326:Fetal Proteins / Q000096:biosynthesis / Q000235:genetics; D018507:Gene Expression Regulation, Developmental; D005796:Genes; D017344:Genes, Insect; D018257:Helix-Loop-Helix Motifs / Q000235:genetics; D006801:Humans; D051379:Mice / Q000235:genetics*; D008817:Mice, Mutant Strains; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000096:biosynthesis / Q000235:genetics; D009687:Nuclear Proteins / Q000096:biosynthesis / Q000235:genetics*; D009928:Organ Specificity; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013045:Species Specificity; D014157:Transcription Factors / Q000096:biosynthesis / Q000235:genetics*; D014158:Transcription, Genetic; D014314:Trisomy
chemical_list: D051792:Basic Helix-Loop-Helix Proteins; D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D005326:Fetal Proteins; D009419:Nerve Tissue Proteins; D009687:Nuclear Proteins; D012333:RNA, Messenger; D014157:Transcription Factors; C417032:SIM2 protein, human; C486578:Sim2 protein, mouse; C089449:sim protein, Drosophila