S Halford

Isolation of a new marker and conserved sequences close to the DiGeorge syndrome marker HP500 (D22S134).

End fragment cloning from a YAC at the D22S134 locus allowed the isolation of a new probe HD7k. This marker detects hemizygosity in two patients previously shown to be dizygous for D22S134. This positions the distal deletion breakpoint in these patients to the sequences within the YAC, and confirms that HD7k is proximal to D22S134. In a search for coding sequences within the region commonly deleted in DGS we have identified a conserved sequence at D22S134. Although no cDNAs have yet been isolated, genomic sequencing shows a short open reading frame with weak similarity to collagen proteins.

Successful targeting of the mouse cystic fibrosis transmembrane conductance regulator gene in embryonal stem cells.

We wish to construct a mouse model for the human inherited disease cystic fibrosis. We describe here the successful targeting in embryonal stem cells of the murine homologue (Cftr) of the cystic fibrosis transmembrane conductance regulator gene, as the first critical step towards this end. The targeting event precisely disrupts exon 10, the site of the major mutation in patients with cystic fibrosis. The targeted cells are pluripotent and competent to form chimaeras.

A NEW POLYMORPHIC LOCUS, D7S411, ISOLATED BY CLONING FROM PREPARATIVE PULSE-FIELD GELS IS CLOSE TO THE MUTATION CAUSING CYSTIC-FIBROSIS

The mutation causing cystic fibrosis (CF) has been localized to the DNA sequence of 700 kb bounded by the loci identified by the markers pMP6d-9 (D7S399) and pJ3.11 (D7S8). A 560-kb fragment obtained after SacII digestion of DNA from a cell line containing this region of human chromosome 7 in a mouse background was separated using pulse-field gel electrophoresis and isolated from the gel. The DNA was digested with BamHI prior to cloning into lambda EMBL3. Approximately 0.1% of the resulting clones contained human repetitive sequences, and 24 such recombinants were studied. Of these, 23 are on chromosome 7; 8 clones were duplicated, and of the 15 different recombinants, 7 are between MET and INT1L1, and a further 7 are between INT1L1 and pMP6d-9, leaving a single marker, pG2, which is between pMP6d-9 and pJ3.11. pG2 recognizes an RFLP with XbaI. A cosmid walk from pG2 has generated a further marker, H80, which recognizes an RFLP with PstI. This new locus (D7S411) divides the remaining region between the CF flanking markers, thereby making it more accessible to fine pulse-field mapping and allowing the precise localization of further clones to this region. Although it is not possible to position the CF locus unequivocally with respect to D7S411, both polymorphic markers at this locus exhibit low but significant linkage disequilibrium with CF, placing the emphasis for the search for the gene on the D7S399 to D7S411 interval of 250 kb.

A novel C2H2 zinc-finger protein gene (ZNF160) maps to human chromosome 19q13.3-q13.4.

The human genome may contain up to 400 genes encoding zinc-finger (ZNF) proteins; a high proportion of those mapped have been localized to human chromosome 19. Heubner and colleagues have mapped 6 cDNAs containing a ZNF motif to 19q, and one to 19p, using somatic cell hybrids. Ten further sequences were regionally assigned by Lichter and colleagues, with a retinoic acid inducible ZNF gene being mapped to 19q13.2-q13.4. Thirty-nine cosmids identified on the basis of cross-hybridization to a ZNF {open_quotes}linker{close_quotes} sequence were mapped by FISH, 24 mapping to 19p and 15 to 19q. However, it is not known which of these sequences are transcribed or encode the cDNAs mentioned above. Forty Kruppel C{sub 2}H{sub 2}-related genes have been mapped to a cluster on 19p12-p13.1. It is interesting that none of these genes is detectable in the mouse or rat genomes, suggesting a relatively recent evolutionary origin for this cluster. 12 refs., 1 fig.