Physical Mapping of the Human Connexin 40 (GJA5), Flavin-Containing Monooxygenase 5, and Natriuretic Peptide Receptor A Genes on 1q21

The human connexin 40 gene (Cx40; HGMW-approved symbol GJA5), a gap junction protein, was mapped previously to 1pter–q12 by analysis of somatic cell hybrids. In the development of a yeast artificial chromosome (YAC) contig at 1q21, a YAC end clone contained the entire 5′-untranslated region and 42 bases of coding region of the Cx40 gene. Using a sequence-tagged site (STS) developed from this sequence as well as amplimers for the natriuretic peptide receptor A (NPR1) and flavin-containing monooxygenase 5 (FMO5) genes, the order NPR1–FMO5–Cx40 was established, with Cx40 being the most telomeric. Single-color FISH using PAC clones containing the Cx40 and NPR1 STSs localized these genes to 1q21.1.     

Mapping of the Human Cysteine-Rich Intestinal Protein GeneCRIP1to the Human Chromosomal Segment 7q11.23

We report here on the mapping of a cDNA encoding for human cysteine-rich heart protein (HCRHP), a counterpart of the murine cysteine-rich intestinal protein CRIP. By somatic cell hybrid analysis and radiation hybrid mapping, we have located the geneCRIP1(HGMW-approved symbol) on the subcentromeric region of the q arm of human chromosome 7, flanking a deletion associated with Williams syndrome.     

Human Somatostatin Receptor Genes: Localization of SSTR5 to Human Chromosome 20p11.2

The gene encoding the somatostatin receptor subtype designated as SSTR5 was mapped to human chromosome 20p11.2 by using fluorescence in situ hybridization to metaphase chromosomes. Fluorescence in situ hybridization using a probe for SSTR5 in combination with probes for neuroendocrine convertase-2 (NEC2), thrombomodulin (THBD), and brain glycogen phosphorylase (PYGB) established a physical order for these loci of 20pter-NEC2-SSTR5-THBD-PYGB-cen.     

Molecular Cloning and in Situ Localization of the Human Contactin Gene (CNTN1) on Chromosome 12q11-q12

Chick contactin/F11 (also known as F3 in mouse) is a neuronal cell adhesion molecule of the immunoglobulin (Ig) gene family that is implicated in playing a role in the formation of axon connections in the developing nervous system. In human brain, contactin was first identified by amino terminal and peptide sequencing of the lentil-lectin-binding glycoprotein Gp135. We now report the isolation and characterization of cDNA clones encoding human contactin. Human contactin is composed of six C2 Ig-domains and four fibronectin type III (FNIII) repeats and is anchored to the membrane via a glycosyl phosphatidylinositol moiety, as shown by PI-PLC treatment of cells transfected with contactin cDNA and metabolic labeling with [3H]-ethanolamine. At the amino acid level, h-contactin is 78% identical to chick contactin/F11 and 94% to mouse F3. Independent cDNAs encoding two putative contactin isoforms were isolated and sequenced: h-contactin 1 cDNA encodes a protein with the amino-terminal sequence of purified Gp135, while the putative h-contactin 2 gene has a deletion of 33 nucleotides that predicts a protein with a shortened amino terminus. Northern analysis with a probe common for both isoforms detects one mRNA species of approximately 6.6 kb in adult human brain. Fluorescence in situ hybridization maps the gene for human contactin to human chromosome 12q11-q12. The h-contactin gene locus is thus in close proximity to homeobox 3, integrin subunit α5, several proto-oncogene genes, a chromosomal breakpoint associated with various tumors, and the gene locus for Stickler syndrome. The cloning of human contactin now permits the study of its role in disorders of the human nervous system.     

Localization of the -Glutamine Synthetase Gene to Chromosome 1q23

Glutamine synthetase (E.C. 6.3.1.2) is expressed throughout the body and plays an important role in controlling body pH and in removing ammonia from the circulation. The enzyme clears -glutamate, the major neurotransmitter in the central nervous system, from neuronal synapses. The enzyme is a very sensitive marker of many disease and aging processes, especially those involving reactive oxygen species. This report describes the localization of the enzyme to chromosome 1 by PCR analysis of a human/rodent somatic cell hybrid panel. We also describe the localization of a recently described pseudogene to chromosome 9. Further localization of the glutamine synthetase gene locus to 1q23 was accomplished by fluorescencein situhybridization. The glutamine synthetase gene was mapped to five CEPH megaYACs between the polymorphic PCR markers D1S117 and D1S466 by analysis of the Whitehead Institute's recently described chromosome 1 contig map.     

Assignment of the Y4Receptor Gene (PPYR1) to Human Chromosome 10q11.2 and Mouse Chromosome 14

The human and mouse genes for the neuropeptide Y₄receptor have been isolated, sequenced, and shown to contain no introns within the coding region of the gene. Nonisotopicin situhybridization and interspecific mouse backcross mapping have localized the genes to human chromosome 10q11.2 and mouse chromosome 14. Five nucleotide variants, which do not alter the protein sequence, have been identified within the coding region of the human receptor gene. The human Y₄subtype is most closely related to the Y₁-receptor subtype (42%), suggesting that it evolved from an ancestral Y₁-like receptor via an RNA-mediated transpositional event.     

Assignment of the βB1 Crystallin Gene (CRYBB1) to Human Chromosome 22 and Mouse Chromosome 5

By using primers complementary to the rat βB1 crystallin gene sequence, we amplified exons 5 and 6 of the orthologous human gene (CRYBB1). The amplified human segments displayed greater than 88% sequence homology to the corresponding rat and bovine sequences.CRYBB1was assigned to the group 5 region in 22q11.2–q12.1 by hybridizing the exon 6 PCR product to somatic cell hybrids containing defined portions of human chromosome 22. The exon 5 and exon 6 PCR products ofCRYBB1were used to localize, by interspecific backcross mapping, the mouse gene (Crybb1) to the central portion of chromosome 5. Three other β crystallin genes (βB2(−1), βB3, and βA4) have previously been mapped to the same regions in human and mouse. We demonstrate that the βB1 and βA4 crystallin genes are very closely linked in the two species. These assignments complete the mapping and identification of the human and mouse homologues of the major β crystallins genes that are expressed in the bovine lens.     

Identification of the Human βA2 Crystallin Gene (CRYBA2): Localization of the Gene on Human Chromosome 2 and of the Homologous Gene on Mouse Chromosome 1

By using primers synthesized on the basis of the bovine βA2 crystallin gene sequence, we amplified exons 5 and 6 of the human gene (CRYBA2). CRYBA2 was assigned to human chromosome 2 by concordance analysis in human × rodent somatic cell hybrids using the amplified PCR products as probe. Regional localization to 2q34-q36 was established by hybridizing the CRYBA2 probe to microcell and radiation hybrids containing defined fragments of chromosome 2 as the only human contribution. The CRYBA2 probe was also used to localize, by interspecific backcross mapping, the mouse gene (Cryba2) to the central portion of chromosome 1 in a region of known human chromosome 2 homology. Finally, we demonstrate that in both species the βA2 crystallin gene is linked but separable from the γA crystallin gene. The βA2 crystallin gene is a candidate gene for human and mouse hereditary cataract.