Structural Characterization and Partial Sequence of the Feline Glucokinase Gene
Dept. Clinical Sciences, College of Veterinary Medicine, Kansas State University
Manhattan, KS, USA
The glucokinase gene (GCK) is primarily expressed in hepatocytes and pancreatic islets, where it is needed for normal glucose metabolism. Genetic polymorphisms and mutations in GCK influence glucose tolerance and can produce a diabetic phenotype. Knowledge of the GCK gene will facilitate molecular and genetic studies of feline glucose metabolism, nutrition, and diabetes. Previous work in our laboratory has elucidated the coding sequence of feline pancreatic GCK cDNA (GenBank #EF121813) but feline GCK has not been studied at the genomic level. The study objective was to obtain the genomic DNA sequence of feline GCK. DNA isolated from peripheral leukocytes from a normal cat and routine PCR and sequencing methods were used to obtain the GCK sequence.
Alignment of overlapping genomic DNA clones (each sequenced 2-4x) generated by PCR using feline-specific primers produced a 3522 bp partial GCK sequence. The feline genomic GCK sequence contained 9 putative exons, which were identified by homology with the known feline pancreatic GCK cDNA sequence, and intervening intronic sequences. Feline exon sequences and lengths were highly conserved compared with human GCK (overall nucleotide identity was 93%); intronic sequences were less conserved. The linear arrangement of exons 2-10 in feline GCK is also found in rodent and human GCK, indicating that gene structure is conserved in this region. In humans and rodents, expression of hepatic- and pancreatic-specific GCK mRNAs is accomplished via use of separate exon 1 isoforms. The existence of multiple exon 1 isoforms was not confirmed by the current study but preliminary analysis shows that feline GCK has a homologue to the human pancreatic specific exon 1B.
In conclusion, the primary nucleotide sequence and organization of the feline GCK gene appears similar to other species. The feline GCK sequence that we have elucidated can serve as a reference sequence for future studies of GCK polymorphisms or mutations within the feline population.