Integration of cytogenetic landmarks into the draft sequence of the human genome

We have placed 7,600 cytogenetically defined landmarks on the draft sequence of the human genome to help with the characterization of genes altered by gross chromosomal aberrations that cause human disease. The landmarks are large-insert clones mapped to chromosome bands by fluorescence in situ hybridization. Each clone contains a sequence tag that is positioned on the genomic sequence. This genome-wide set of sequence-anchored clones allows structural and functional analyses of the genome. This resource represents the first comprehensive integration of cytogenetic, radiation hybrid, linkage and sequence maps of the human genome; provides an independent validation of the sequence map and framework for contig order and orientation; surveys the genome for large-scale duplications, which are likely to require special attention during sequence assembly; and allows a stringent assessment of sequence differences between the dark and light bands of chromosomes. It also provides insight into large-scale chromatin structure and the evolution of chromosomes and gene families and will accelerate our understanding of the molecular bases of human disease and cancer.

Characterization of the mouse collectin gene locus

Three of the four known mouse collectin genes have been mapped to chromosome 14. To further characterize the spatial relationship of these genes, a bacterial artificial chromosome (BAC) library of mouse chromosome 14 was screened using mouse surfactant protein (SP)-A and -D complementary DNAs (cDNAs). One large clone hybridized to both SP-A and SP-D cDNAs and was found by polymerase chain reaction (PCR) to contain sequences from one of the mouse mannose-binding lectin genes (Mbl1). We used Southern mapping and subcloning of overlapping restriction fragments to characterize the gene locus. Mapping was confirmed by fluorescent in situ hybridization of fiber-stretched BAC DNA and by Southern hybridization of restriction endonuclease-digested and PCR-amplified genomic DNA. We found that the SP-A, Mbl1, and SP-D genes reside contiguously within a 55-kb region. The SP-A and Mbl1 genes are in the same 5' to 3' orientation and 16 kb apart. The SP-D gene is in the opposite orientation to the two other collectin genes, 13 kb away from the 3' end of the Mbl1 gene. The mouse SP-D gene had not previously been characterized. We found its size (13 kb) and organization to be similar to that of human SP-D. Exon I is untranslated. The second exon is a hybrid exon that contains signal for initiation of translation, signal peptide, N-terminal domain, and the first seven collagen triplets of the collagen-like domain of the protein. Four short exons (III through VI) encode the collagen-like domain of the protein, and exons VII and VIII the linking and the carbohydrate-recognition domains, respectively.