In the context of a hunt for a postulated hormone that is tissue-mass inhibiting and reproductively associated, there is described probable relatedness to a granin protein. A 7–8 kDa polypeptide candidate (gels/MS) appeared in a bioassay-guided fractionation campaign involving sheep plasma. An N-terminal sequence of 14 amino acids was obtained for the polypeptide by Edman degradation. Bioinformatics and molecular biology failed to illuminate any ovine or non-ovine protein which might relate to this sequence. The N-terminal sequence was synthesized as the 14mer EPL001 peptide and surprisingly found to be inhibitory in an assay in vivo of compensatory renal growth in the rat and modulatory of nematode fecundity, in line with the inhibitory hormone hypothesis. Antibodies were raised to EPL001 and their deployment upheld the hypothesis that the EPL001 amino acid sequence is meaningful and relevant, notwithstanding bioinformatic obscurity. Immunohistochemistry (IHC) in sheep, rodents and humans yielded staining of seeming endocrine relevance (e.g. hypothalamus, gonads and neuroendocrine cells in diverse tissues), with apparent upregulation in certain human tumours (e.g. pheochromocytoma). Discrete IHC staining in Drosophila melanogaster embryo brain was seen in glia and in neuroendocrine cells, with staining likely in the corpus cardiacum. The search for the endogenous antigen involved immunoprecipitation (IP) followed by liquid chromatography and mass spectrometry (LC–MS). Feedstocks were PC12 conditioned medium and aqueous extract of rat hypothalamus—both of which had anti-proliferative and pro-apoptotic effects in an assay in vitro involving rat bone marrow cells, which inhibition was subject to prior immunodepletion with an anti-EPL001 antibody—together with fruit fly embryo material. It is concluded that the mammalian antigen is likely secretogranin II (SgII) related. The originally seen 7–8 kDa polypeptide is suggested to be a new proteoform of secretogranin II of ∼70 residues, SgII-70, with the anti-EPL001 antibody seeing a discontinuous epitope. The fly antigen is probably Q9W2X8 (UniProt), an uncharacterised protein newly disclosed as a granin and provisionally dubbed macrogranin I (MgI). SgII and Q9W2X8 merit further investigation in the context of tissue-mass inhibition.

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In this study using Caenorhabditis elegans, we have been able to suppress (> 60%) and enhance (> 40%) fecundity (number of offspring) while extending lifespan by a fifth, by administering synthetic peptides to the aqueous medium in which the nematodes were maintained. Untreated control adults fed live bacteria had significantly more offspring (17 vs 10 larvae each) than those fed dead bacteria. Average lifespan and time for 50% of the worms to die were the same at approximately 10 days, but there was a significant difference in terms of 100% mortality (28 vs 19 days). A reduction in fecundity of 30-40% occurred when a 14-mer peptide, EPL030, was administered to the worms' aqueous medium. The effect was dose-dependent across the range 0.1-10 mu M day(-1) of medium, but since the worms were fed live bacteria interpretation was problematic: was the effect direct or indirect? However, the anti-fecundity effect was reproduced in worms fed dead bacteria, when the test compound was administered at I mu M day(-1) of aqueous medium. The mean number of larvae produced in three groups: untreated controls, EPL030 and EPL001 (an anagrammatical version of EPL030 used as a comparator), were, respectively, 17, 6 (-64%) and 24 (+43%). Average lifespans were 8.7, 10.7 (+23%) and 10.3 days (+18%). Fluorescence localisation studies using a close analogue of the fecundity-suppressing EPL030 revealed a distribution that was generalised and uninformative. The fecundity-enhancing EPL001 concentrated in the genital tract. Caenorhabditis elegans is a potentially useful testbed for fecundity and lifespan studies using exogenous agents. The use of an aqueous medium and dead bacteria as food simplifies both the protocol and interpretation of results

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