Camelid Peptidomics: Logical Sequel to Transcriptomics

One of the striking examples of plasticity in nature is the ability of one-humped Arabian camel (Camelus dromedarus) to survive extended periods of water deprivation and to tolerate water loss of up to 30% its body weight. The brain regulates water balance through the hypothalamo-neurohyophysial system (HNS). In the camel, the HNS is thought to go into a state of permanent activation during arid summers in preparation for the prospect of water deprivation.  Progress in the sequencing of Arabian camel genome and HNS transcriptome has laid the foundation for a functional analysis of gene products mediating this unique physiology in this species. However, the immense challenge is due to the complexity of molecular readout: a single gene can produce many products as a result of SNPs, alternative gene splicing, post-translational processing of precursor proteins, and chemical post-translational modifications to cleaved peptides that often cannot be inferred from genomic data. To determine the actual gene products, neuropeptides and hormones which mediate this vital physiology, direct measurements at peptide level are invaluable. Mass spectrometry-based direct analysis of endogenous peptides, e.g. peptidomics, is capable of characterizing of highly diverse peptide complement in camel HNS. Here, we used this approach to de novo sequence hundreds of peptides in camel HNS (pituitary and supraoptic nucleus, SON). Sequence tags were identified against our custom camel transcriptome database. The obtained peptidomics data can be used to gain insights into evolutionary adaptation among camels and to advance the functional study of the seasonal adaptations in the camel HNS.