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| A cDNA encoding pro-opiodmelanocortin (POMC) was cloned from pituitary of the rare minnow ( Gobiocypris rarus), a small freshwater fish endemic to China ，by polymerase chain reaction(RT-PCR) and rapid amplification of cDNA ends (RACE). Data showed that, the predicted rare minnow POMC cDNA (rmPOMC) consisted of 844bp with a 666bp ORF coding for the following sequences flanked by proteolytic cleavage sites: signal peptide (SP, Met1–Ala28), N-terminal peptide (Gln29–His105), ACTH (Ser108–Met146), α-MSH ( Ser108–Gal121), CLIP (Pro126–Met146), β-LPH (Glu149–His221), γ-LPH (Glu149– Ser186), β-MSH (Asp 170–Ser186), β-endorphin (β-EP, Tyr189–Gln221). Sequence analysis showed no region homologous to γ-MSH/ joining peptide (a tetrapod pomc feature ) was found. Amino acid sequence shares a highest similarity with POMC-Ⅰand POMC-Ⅱof common carp (92.4%) according to homologous alignment.
Pituitary and extra-pituitary expression were studied by RT-PCR and in situ hybridization. rmPOMC positive cells mainly located in rostral pars distails (RPD) and pars intermedia(PI). Otherwise, there were some rmPOMC positive cells detected in PPD too according to in situ hybridization. In the extra-pituitary tissues, positive signals were observed in brain, intestine, gonad, hepatopancreas, spleen and gill by RT-PCR analysis.
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| Keywords:pro-opiomelancortin(POMC);cDNA cloning;pituitary location;extra-pituitary expression;Rare Minnow (Gobiocypris rarus) |
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