ISOLATION OF COSMID AND CDNA CLONES IN THE REGION SURROUNDING THE BTKGENE AT XQ21.3-Q22

A regional physical and transcription map involving yeast artificial c hromosomes (YACs), cosmids, and cDNAs has been constructed for Xq21.3- q22 around the gene BTK (formerly atk or BPK) defective in X-linked ag ammaglobulinemia (XLA). With a positional cloning strategy employing d irect cDNA selection, novel cDNAs were found to cluster in the region of approximately 100 kb flanking the XLA and alpha-galactosidase A loc i. While these widely expressed transcripts are in the area known to c ontain CpG islands, a less evolutionarily conserved gene, located more than 130 kb distal of DXS178, maps to cosmid clones that could not be digested with rare-cutting restriction enzymes. The presence of trans cribed sequences flanking the BTK allowed us to investigate their invo lvement in complex XLA phenotypes. Southern blot analysis using cDNA c lones isolated from this region permitted us to exclude a contiguous d eletion syndrome as an underlying defect in three patients with XLA an d associated growth hormone deficiency. A single XLA patient with tors ion dystonia and cosegregating X-linked deafness has been found with a deletion in the 3' part of BTK extending centromerically into the fla nking expressed sequence DXS1274E. This suggests a possible involvemen t of the DXS1274E in this phenotype. The GenBank accession numbers for novel cDNA sequences are as follows: DXS1269E (L20773), DXS1271E (UO1 923), DXS1273E (UO1925), and DXS1274E (UO1922). (C) 1994 Academic Pres s, Inc.