Over the past decade, mass spectrometry has become a prominent technique for identifying
peptide hormones. In crustaceans, studies directed at characterizing the
peptide complements present in neuroendocrine structures have generally involved the isolation of tissue from a large number of individuals, which are pooled, extracted, purified, and then analyzed via chromatographic techniques coupled with mass spectrometry. While this approach provides information on the
peptides present in the population of animals used as the tissue source, data on the
peptide complement present in any individual animal are lost. Direct tissue matrix assisted
laser desorption/ionization Fourier transform mass spectrometry (MALDI-FTMS) of single tissues has the potential to identify differences in
peptide expression between individuals. Here, we have used direct tissue MALDI-FTMS of individual sinus glands (SGs) to show that the four
isoforms of
crustacean hyperglycemic hormone precursor-related
peptide (CPRP) identified previously from pooled
Cancer productus SGs (i.e. Fu, Q., Christie, A.E., Li, L. 2005. Mass spectrometric characterization of
crustacean hyperglycemic hormone precursor-related
peptides (CPRPs) from the sinus gland of the crab,
Cancer productus.
Peptides 26, 2137-2150.) are differentially distributed in conserved patterns among individual crabs. Of the crabs examined, approximately 61% of the individuals possessed Capr-CPRP I and II, but not III or IV, approximately 26% Capr-CPRP I, II and III, but not IV, and approximately 13% Capr-CPRP I, II and IV, but not III. Our findings set the stage for future molecular investigations on the origin(s) of this individual-specific variation in CPRP
complement, as well as investigations of the function and regulation of the individual
isoforms. These data also lend a cautionary note to the assumption that the
peptides identified via pooled tissues reveal an accurate picture of the
peptides present in any given individual.