Neuropeptidome of the Hypothalamus and Pituitary Gland of Indicine × Taurine Heifers: Evidence of Differential Neuropeptide Processing in the Pituitary Gland before and after Puberty

Puberty in cattle is regulated by
an endocrine axis, which includes
a complex milieu of neuropeptides in the hypothalamus and pituitary
gland. The neuropeptidome of hypothalamic–pituitary gland tissue
of pre- (PRE) and postpubertal (POST) Bos indicus-influenced heifers was characterized, followed by quantitative analysis
of 51 fertility-related neuropeptides in these tissues. Comparison
of peptide abundances with gene expression levels allowed assessment
of post-transcriptional peptide processing. On the basis of classical
cleavage, 124 mature neuropeptides from 35 precursor proteins were
detected in hypothalamus and pituitary gland tissues of three PRE
and three POST Brangus heifers. An additional 19 peptides (cerebellins,
PEN peptides) previously reported as neuropeptides that did not follow
classical cleavage were also identified. In the pre-pubertal hypothalamus,
a greater diversity of neuropeptides (25.8%) was identified relative
to post-pubertal heifers, while in the pituitary gland, 38.6% more
neuropeptides were detected in the post-pubertal heifers. Neuro-tissues
of PRE and POST heifers revealed abundance differences (p < 0.05) in peptides from protein precursors involved in packaging
and processing (e.g., the granin family and ProSAAS) or neuron stimulation
(PENK, CART, POMC, cerebellins). On their own, the transcriptome data
of the precursor genes could not predict the neuropeptide profile
in the exact same tissues in several cases. This provides further
evidence of the importance of differential processing of the neuropeptide
precursors in the pituitary before and after puberty.