Cloning of cDNA and Genomic DNA Encoding Human Type XVIII Collagen and Localization of the α1(XVIII) Collagen Gene to Mouse Chromosome 10 and Human Chromosome 21

Types XV and XVIII collagen belong to a unique and novel subclass of the collagen superfamily for which we have proposed the name the MULTIPLEXIN family. Members of this class contain polypeptides with multiple triple-helical domains separated and flanked by non-triple-helical regions. In this paper, we report the isolation of human cDNAs and genomic DNAs encoding the α1(XVIII) collagen chain. Utilizing a genomic clone as probe, we have mapped the COL18A1 gene to chromosome 21q22.3 by fluorescence in situ hybridization. In addition, using an interspecific backcross panel, we have shown that the murine Col18a1 locus is on chromosome 10, close to the loci for Col6a1 and Col6a2.     

MappingTNNC1, the Gene That Encodes Cardiac Troponin I in the Human and the Mouse

We have mapped the TNNC1 gene, whose protein product is the cardiac TnI protein. TnI is one of the proteins that makes up the troponin complex, which mediates the response of muscle to calcium ions. The human TNNC1 locus had been assigned to a large region of chromosome 19, and we have refined the mapping position to the distal end of the chromosome by amplification of DNAs from a chromosome 19 mapping panel. We have also mapped the mouse Tnnc1 locus, by following the segregation of an intron sequence through DNAs from the European Interspecific Backcross. Tnnc1 maps close to the centromere on mouse chromosome 7.     

Characterization of a Widely Expressed Gene (LUC7-LIKE; LUC7L) Defining the Centromeric Boundary of the Human α-Globin Domain

We have identified the first gene lying on the centromeric side of the α-globin gene cluster on human 16p13.3. The gene, called 16pHQG;16 (HGMW-approved symbol LUC7L), is widely transcribed and lies in the opposite orientation with respect to the α-globin genes. This gene may represent a mammalian heterochromatic gene, encoding a putative RNA-binding protein similar to the yeast Luc7p subunit of the U1 snRNP splicing complex that is normally required for 5′ splice site selection. To examine the role of the 16pHQG;16 gene in delimiting the extent of the α-globin regulatory domain, we mapped its mouse orthologue, which we found to lie on mouse chromosome 17, separated from the mouse α-cluster on chromosome 11. Establishing the full extent of the human 16pHQG;16 gene has allowed us to define the centromeric limit of the region of conserved synteny around the human α-globin cluster to within an 8-kb segment of chromosome 16.