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INTRODUCTION The cGMP phosphodiesterase beta-subunit (PDEB), when associated with a cGMP phosphodiesterase alpha-subunit, forms a functional holoenzyme that participates in the processes of transmission and amplification of the visual signal in rod cells. Both subunits have two cGMP-binding sites (GAF) in the N-terminal half and a catalytic domain (PDEase) in the C-terminal portion. The PDEB gene (4p16.3) presents with at least 28 reported mutations causing hereditary retinitis pigmentosa (RP), 27 polymorphic sites, and seven regions in conflict. ‘Regions in conflict’ are those with more than one version of the nucleotide sequence encoded by a specific DNA region. The conflict at site 698 in the PDEB protein is caused by the putative assignment of the amino acids isoleucine (Ile) or tyrosine (Tyr), coded by ATC and TAC triplets, respectively. Both triplets differ in the two first nucleotides (AT or TA), corresponding to positions 71 and 72 of exon 17, located in the PDEase domain of PDEB. Weber and co-workers first reported the complete sequence of PDEB as having AT in region 698, but then Collins and co-workers reported TA for the same region. Both studies were performed in clones of genomic DNA or cDNA, respectively. To date, any one of the seven sites in conflict of the human PDEB have been resolved. We carried out a survey to resolve the conflict site 698, by studying the nucleotides sequence of human genome samples directly. We analyzed PCR products of exon 17 of one hundred Mexican individuals for recognize TAC triplet by restriction enzyme assay and by sequencing.

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2006-09-28   |   1,428 visitas   |   1 valoraciones

Vol. 58 Núm.4. Julio-Agosto 2006 Pags. 359-361 Rev Invest Clin 2006; 58(4)