NORMAL GENOMIC

• Kamei M, Webb GC, Young IG, Campbell HD
• SOLH, a human homologue of the Drosophila melanogaster small optic lobes gene is a member of the calpain and zinc-finger gene families and maps to human chromosome 16p13.3 near CATM (cataract with microphthalmia).
• Genomics. 1998; 51: 197-206
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• Mutations in the Drosophila melanogaster small optic lobes (sol) gene cause a sever reduction in the neuropiles of the medulla and lobula complexes of the adult optic lobes. The predicted protein product of sol contains zinc-finger-like repeats, a calpain-like protease domain, and a C-terminal region of unknown function. We have isolated human brain cDNA for SOLH, a human homologue of sol. The human SOLH gene consists of 14 exons distributed over more than 45 kb of genomic DNA. The encoded SOLH protein of 1086 amino acids has strong similarity to the D. melanogaster protein. The calpain-like domain and C-terminal region are highly conserved (58% identity), and similar Cys2-Cys2 zinc fingers are present in the N-terminal region. A reported Caenorhabditis elegans homologue contains the calpain domain and C-terminal region, but appears to lack the zinc finger region. A single copy of the zinc finger sequence is present in adjacent C. elegans genomic cosmid DNA sequence, and we show that it is part of the C. elegans sol-like transcript. Northern analysis of human tissues revealed a SOLH transcript of approximately 5 kb that was strongest in human brain. We have mapped the SOLH gene to chromosome 16p13.3 by in situ hybridization. SOLH is a candidate gene for CATM (hereditary cataracts with microphthalmia), which maps in this region.

• Bornemann D, Miller E, Simon J
• The Drosophila Polycomb group gene Sex comb on midleg (Scm) encodes a zinc finger protein with similarity to polyhomeotic protein.
• Development. 1996; 122: 1621-30
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• The Sex comb on midleg (Scm) gene is a member of the Polycomb group (PcG) of genes in Drosophila melanogaster. The PcG genes encode transcriptional repressors required for proper spatial expression of homeotic genes. We report the isolation of new Scm mutations and the molecular characterization of the Scm gene. Scm mRNA is expressed maternally, at peak levels in early embryos and then at lower levels throughout the remainder of development. Scm encodes a putative zinc finger protein of 877 amino acids. Scm protein is similar to polyhomeotic, another member of the PcG, both in the zinc finger region and in a separate C-terminal domain of 60 amino acids, which we term the SPM domain. Sequence analysis of an Scm mutant allele suggests a functional requirement for the SPM domain. Scm protein also bears homology in multiple domains to a mouse protein, Rae-28 (Nomura, M., Takihara, Y. and Shimada, K. (1994) Differentiation 57,39-50) and to a fly tumor suppressor protein, the product of the lethal(3)malignant brain tumor gene (Wismar, J. et al., (1995) Mech. Dev. 53, 141-154). Possible functional relationships among these proteins and potential biochemical roles for Scm protein in PcG repression are discussed.