Physical linkage of expressed sequence tags (ESTs) to polymorphic markers on the X chromosome.

Expressed sequence tags (ESTs) can in principle serve as specialized sequence tagged sites (STSs) to assemble a functional map of the human genome. The strategy of physically linking ESTs to the nearest genetic linkage markers should provide specific candidate genes for the X-linked diseases associated with these markers or loci. Therefore, 19 ESTs assigned to the X chromosome in the Genome Database (GDB) were analyzed. Eighteen were confirmed to be X-specific and were localized to regions of the X chromosome using a panel of somatic cell hybrids. Localization was then refined by positioning them on yeast artificial chromosome (YAC)-based maps. Seventeen ESTs identified cognate YACs by PCR screening and 12 of the ESTs have been assembled in YAC contigs containing polymorphic and other X chromosomal markers. Two of them also produced syntenically equivalent products in mouse. Thus localizing ESTs relative to polymorphic markers will help to assemble an integrated physical and transcriptional map of the chromosome and provide candidates for disease-gene searches.