Abstract
Abstract: :
Purpose: An organ–specific Expression Sequence Tag (EST) library provides a snapshot of genes expressed and serves as a baseline for comparison to altered expression during disease. Surprisingly, no lacrimal gland EST database exists – an observation made obvious after cDNA cloning of lacrimal–specific lacritin (J. Mol. Biol. 310:137,2001). In collaboration with NEIBank, we report the development of the first human and mouse databases. Methods: Male (75 yrs) and female (51 yrs) normal human lacrimal glands were collected anonymously by the Mid–Atlantic Division of CHTN. Post–mortem times to freezing were 6 and 7.75 hrs, respectively. The samples were histologically excellent with no evidence of autoimmune disease. Murine lacrimal glands were collected from approx. 80 C57Bl6 males (7 – 8 wk) and immediately frozen. cDNAs were prepared from purified polyA+ RNAs, directionally cloned into pCMVSPORT6, sequenced by the NIH Intramural Sequencing Center, and then analyzed using GRIST (GRouping and Identification of Sequence Tags). Results: Sequencing of 6000 human and 3000 mouse cDNAs revealed an unusual number of named sequences with no known function, particularly in the mouse library. The most abundant genes differed between the two species. Among the most frequent human ESTs were lysozyme, PROL4, lipocalin 1, lactotransferrin, PROL1 and lacritin. In mouse, odorant binding protein 1a, 11kDa secreted protein, salivary protein1 and three apparently novel gene products predominated. Human chromosomal arms 1p (65 genes), 12q (51 genes), 17q (44 genes), 1q (41 genes), and 14q (40 genes) harbored most lacrimal genes; the highest expressors derived from 12q (257 clones), 12p (158 clones), and 9q (147 clones). The 12q gene cluster includes lacritin. Clusters centered at 69 and 54Mb on 12q, 86 Mb on 1p, and 62, 73, 74 and 80 Mb on 17q are all demonstrated or predicted to be telomeric in the mouse, a chromosomal location where new genes most frequently arise. Clustering of genes suggests related catabolic functions and shared aspects of transcriptional regulation. Conclusions: Both EST databases reveal an array of known or little known genes, with an uneven chromosomal distribution suggesting regions of gene coregulation. The pattern also provides intriguing and unique hints into how this interesting exocrine gland may have evolved.
Keywords: lacrimal gland • gene/expression • genetics