Alternative Splicing Dynamics of the Hypothalamus-Pituitary-Ovary Axis During Pubertal Transition in Gilts

Abstract

The timing of puberty in mammals marks the point at which reproduction becomes possible. Abnormalities in the timing of puberty may exert a series of negative effects on subsequent health outcomes. Alternative splicing (AS) has not only emerged as a significant factor in the transcription of genes but it is also reported to play a role in the timing of puberty. However, to date, the changes and dynamics of AS during the onset of puberty is extremely seldom explored. In the present study, we used gilts as a research model to investigated the dynamics of AS and differentially expressed AS (DEAS) events within the hypothalamus-pituitary-ovary (HPO) axis across pre-, in-, and post-puberty. We detected 3,390, 6,098, and 9,085 DEAS events in the hypothalamus, pituitary, and ovary when compared across pre-, in-, and post-pubertal stages, respectively. Within the entire HPO axis, we also identified 22,889, 22,857, and 21,055 DEAS events in the pre-, in-, and post-pubertal stages, respectively. Further analysis revealed that the differentially spliced genes (DSGs) associated with staged DEAS events were likely to be enriched in the oxytocin signaling pathway, thyroid hormone signaling pathway, GnRH signaling pathway, and oocyte meiosis signaling pathway. The DSGs associated with DEAS events across the entire HPO axis were enriched in endocytosis signaling pathway, the MAPK signaling pathway, and the Rap1 signaling pathway. Moreover. the ASs of TAC1, TACR3, CYP19A1, ESR1, ESRRA, and FSHR were likely to regulate the functions of the certain HPO tissues during the onset of puberty. Collectively, the AS dynamics and DEAS events were comprehensively profiled in hypothalamus, pituitary, and ovary across the pre-, in-, and post-pubertal stages in pigs. These findings may enhance our knowledge of how puberty is regulated by AS and shed new light on the molecular mechanisms underlying the timing of puberty in mammals.

Keywords: alternative splicing; differentially spliced genes; gilts; hypothalamus-pituitary-ovary axis; puberty.

FIGURE 1

Overview of alternative splicing (AS) events in the pubertal hypothalamus–pituitary–ovary (HPO) axis. The number of AS events in the hypothalamus, pituitary, and ovary of gilts during pre-, in-, and post-pubertal stages.

FIGURE 2

Staged differentially expressed alternative splicing (DEAS) events in the hypothalamus–pituitary–ovary (HPO) axis. Pairwise comparisons detected DEAS events in the hypothalamus (A), pituitary (B), and ovary (C) of pre-, in-, and post-pubertal tissues.

FIGURE 3

Characterization of the parental genes for staged differentially expressed alternative splicing (DEAS) events. The number of parental genes of the DEAS detected in the hypothalamus (A), pituitary (B), and ovary (C). Upset plot of different types of DEAS events, and their parent genes, in the hypothalamus (D), pituitary (E), and ovary (F). The abscissa is the number of genes that have occurred corresponding to AS, the ordinate represents the number of genes that occurred multiple AS. One gene may have up to six types of alternative splicing.

FIGURE 4

KEGG analysis of differentially spliced genes in three tissues from gilts (FDR < 0.05).

FIGURE 5

Tissular differentially expressed alternative splicing (DEAS) events during pubertal transition. Pairwise comparison–detected DEAS events were detected pre-puberty (A), in-puberty (B), and post-puberty (C) in the hypothalamus, pituitary, and ovary.

FIGURE 6

KEGG analysis of tissular differentially spliced genes and a network of splicing factors. KEGG analysis of DEAS in pre-puberty (A), in-puberty (B), and post-puberty (C) (FDR < 0.05). (D) Network of splicing factors (SFs) and pubertal genes of specific AS. Blue nodes represent stage-specific; purple nodes represent tissue-specific; and red nodes represent both stage- and tissue-specific AS.

FIGURE 7

RT-PCR of alternative splicing (DEAS) events for validation. (A) DEAS of TAC1 in pre-, in-, and post-pubertal hypothalamus. (B) DEAS of TACR3 in pre-pubertal ovary and hypothalamus. (C) DEAS of ESR1 in pre- and post-pubertal ovary.