• Animal cells and systems
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• v.4 no.4
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• pp.367-373
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• 2000

In the present study we determined if NELL2, a neural tissue-specific protein containing 6 epidermal growth factor (EGF)-like repeat domains, plays an important role in the regulation of puberty initiation in the rat hypothalamus. We origin811y found that NELL2 is a new estrogen-responsive gene in hypothalami derived from estrogen-sterilized and control rats using a PCR differential display. In the 40-day-old female rat hypothalamus, NELL2 was up-regulated by neonatal estrogen treatment. In situ hybridization histochemistry showed that NELL2 is very abundant in the ventromedial hypothalamic nucleus that is responsible for the control of sex behavior. NELL2 mRNA level in the medial basal hypothalamus showed a dramatic increase before female puberty onset, which suggests that NELL2 may be involved in the process regulating female puberty onset. We attemped to block NELL2 synthesis with intracerebroventricular injection of an antisense oligodeoxynucleotide (ODN) to the NELL2 mRNA, and examined its effect on the puberty onset of the female rat. The antisense ODN significantly delayed puberty initiation determined by vaginal opening. In summary, NELL2 may play an important role in the regulation of female puberty onset.

• Asian-Australasian Journal of Animal Sciences
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• v.29 no.9
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• pp.1309-1313
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• 2016

Metabolic signals and the state of energy reserves have been shown to play a crucial role in the regulation of reproductive function. This study was carried out to investigate the effects of dietary glucose levels on puberty onset in gilts. Weight-matched, landrace gilts (n = 36) $162{\pm}3days$ old, weighing about $71.05{\pm}4.53kg$, were randomly assigned to 3 dietary treatment groups of 12 gilts each. The trial lasted until the onset of puberty. Gilts in each group were supplied with diets containing different levels of glucose as follows: i) starch group (SG) was free of glucose, contained 64% corn derived starch; ii) low-dose group (LDG) contained 19.2% glucose and 44.8% corn derived starch; iii) high-dose group (HDG) contained 30% glucose and 30% corn derived starch. Results indicated: i) The growth performance of gilts were not affected by the addition of glucose, but the age of puberty onset was advanced significantly (p<0.05); ii) Compared with the SG, the concentration of insulin significantly increased before puberty in HDG (p<0.05); iii) There was no difference in serum progesterone (P) levels amongst the different feed groups, however, levels of estradiol ($E_2$), luteinizing hormone, and follicle-stimulating hormone were significantly higher at puberty onset in HDG (p<0.05). Overall, our findings indicate that glucose supplementation significantly advances puberty onset, which can have practical purposes for commercial breeding.

• Animal cells and systems
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• v.3 no.3
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• pp.319-329
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• 1999

Onset of female puberty follows a series of prepubertal cellular and molecular events including changes of synaptic plasticity, synthetic and releasing activity and gene expression. Dramatic increase of gonadal steroid level is one of the most prominent changes before the onset of puberty. Based on the importance of steroid feedback upon the hypothalamus, we adopted an estrogen sterilized rat (ESR) model where 100 ng of 17$\eta$-estradiol were administered into neonatal pubs for 7 days after birth. To identify genes involved in the onset of female puberty, we applied PCR differential display using RNA samples derived from ESR and control rat hypothalami. About 100 out of more than 1000 RNA species examined displayed differential expression patterns between a 60-day old control rat and ESR. Sequence analysis of differentially amplified PCR products showed homology with genes such as mouse kinesin superfamily-associated protein 3 (KAP3) and several cDNAs previously described by others in mouse and human tissues. Several gene products such as 2-1 and 8-1 corresponded to novel DNA sequences. We analyzed mRNA levels of KAP3, 2-1 and 8-1 genes in the hypothalami derived from neonatal, 6-, 28-, 31-, and 40-day old rats. Northern blot analysis showed that mRNAs of KAP3, 2-1 and 8-1 genes were markedly increased before the initiation of puberty. Neonatal treatment of estrogen clearly inhibited prepubertal increases in KAP3, 2-1 and 8-1 mRNA levels. Therefore, these genes may play important roles in the initiation of hypothalamic puberty. In addition, intracerebroventricular (icv) injection of antisense KAP3 oligodeoxynucleotide (ODN) clearly delayed puberty initiation determined by vaginal opening, which further confirmed that KAP3 plays an important role in the regulation of puberty initiation.

• Asian-Australasian Journal of Animal Sciences
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• v.32 no.1
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• pp.23-30
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• 2019

Objective: Recent studies have demonstrated that lin-28 homolog B (LIN28B)/miRNA let-7 (let-7) plays a role in the regulation of pubertal onset in mammals. However, the role of LIN28B/let-7 in the onset of ovine puberty remains unknown. We cloned the Duolang sheep Lin28B cDNA sequence, detected the expression change of LIN28B, let-7a and let-7g in hypothalamus, pituitary and ovary tissues at three different pubertal stages. Methods: The reverse transcriptase polymerase chain reaction (RT-PCR) was used to clone the cDNA sequence of LIN28B gene from Duolang sheep and the bioinformatics methods were applied to analyze the amino acid sequence of LIN28B protein. The mRNA expression levels of the LIN28B gene at different pubertal stages were examined by real time RT-PCR. Results: LIN28B cDNA of Duolang sheep was cloned, and two transcripts were obtained. The amino acid sequence of transcript 1 shares 99.60%, 98.78%, and 94.80% identity with those of goat, wild yak and pig, respectively. Strong LIN28B mRNA expression was detected in the hypothalamus, pituitary, ovary, oviduct and uterus, while moderate expression was found in the liver, kidney, spleen and heart, weak expression was observed in the heart. No expression was found in the lungs. Quantitative real-time PCR (QPCR) and western-blot analysis revealed that the LIN28B was highly expressed in the hypothalamus and ovary at prepuberty stages, and this expression significantly decreased from the prepuberty to puberty stages (p<0.05). Markedly increased levels of mRNA expression were detected in the pituitary from prepuberty to puberty (p<0.05) and then significantly decreased from puberty to post-puberty (p<0.05). The expression levels of let-7a and let-7g showed no significant changes among different pubertal stages (p>0.05). Conclusion: These results provided a foundation for determining the functions of LIN28B/let-7 and their role in the onset of sheep puberty.

• Molecules and Cells
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• v.22 no.1
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• pp.30-35
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• 2006

Munc18, a mammalian homolog of C. elegans Unc, is essential for neurotransmitter release. The aim of this study was to identify estrogen-dependent expression of Munc18-1 and its role in the regulation of glutamate release for puberty onset. Hypothalamic munc18-1 mRNA levels were significantly increased by estrogen treatment in ovariectomized, immature female rats. During pubertal development, the munc18-1 mRNA levels dramatically increased between the juvenile period and the anestrous phase of puberty. Intracerebroventricular administration of an antisense oligodeoxynucleotide against munc18-1 mRNA significantly decreased glutamate release and delayed the day of puberty onset. These results suggest that Munc18-1, expressed in an estrogen-dependent manner, plays an important role in the onset of female puberty via the regulation of glutamate release.

• Development and Reproduction
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• v.13 no.3
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• pp.183-190
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• 2009

In mammals, puberty is a dynamic transition process from infertile immature state to fertile adult state. The neuroendocrine aspect of puberty is started with functional activation of hypothalamus-pituitary-gonadal hormone axis. The timing of puberty can be altered by many factors including hormones and/or hormone-like materials, social cues and metabolic signals. For a long time, attainment of a particular body weight or percentage of body fat has been thought as crucial determinant of puberty onset. However, the precise effect of high-fat (HF) diet on the regulation of hypothalamic GnRH neuron during prepubertal period has not been fully elucidated yet. The present study was undertaken to test the effect of a HF diet on the puberty onset and hypothalamic gene expressions in immature female rats. The HF diet (45% energy from fat, HF group) was applied to female rats from weaning to around puberty onset (postnatal days, PND 22-40). Body weight and vaginal opening (VO) were checked daily during the entire feeding period. In the second experiment, all animals were sacrificed on PND 36 to measure the weights of reproductive tissues. Histological studies were performed to assess the effect of HF diet feeding on the structural alterations in the reproductive tissues. To determine the transcriptional changes of reproductive hormone-related genes in hypothalamus, total RNAs were extracted and applied to the semi-quantitative reverse transcription polymerase chain reaction (RT-PCR). Body weights of HF group animals tend to be higher than those of control animals between PND 22 and PND 31, and significant differences were observed PND 32, PND 34, PND 35 and PND 36 (p<0.05). Advanced VO was shown in the HF group (PND $32.8{\pm}0.37$ p<0.001) compared to the control (PND $38.25{\pm}0.25$). The weight of ovaries (p<0.01) and uteri (p<0.05) from HF group animals significantly increased when compared to those from control animals. Corpora lutea were observed in the ovaries from the HF group animals but not in control ovaries. Similarly, hypertrophy of luminal and glandular uterine epithelia was found only in the HF group animals. In the semi-quantitative RT-PCR studies, the transcriptional activities of KiSS-1 in HF group animals were significantly higher than those from the control animals (p<0.001). Likewise, the mRNA levels of GnRH (p<0.05) were significantly elevated in HF group animals. The present study indicated that the feeding HF diet during the post-weaning period activates the upstream modulators of gonadotropin such as GnRH and KiSS-1 in hypothalamus, resulting early onset of puberty in immature female rats.

• Journal of Animal Reproduction and Biotechnology
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• v.36 no.1
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• pp.25-34
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• 2021

Kisspeptin is a key player in the central control of reproductive axis. Central administration of kisspeptin has been shown to advance puberty in rats. Stimulation of hypothalamic GnRH pulse generating mechanism by kisspeptin has been proposed to be the mechanism behind the onset of puberty. We hypothesized that chronic high doses of kisspeptin administration suppresses the reproductive axis and hence delays the pubertal onset. Hence, we investigated the effect of peripheral administration of chronic high doses of kisspeptin on pubertal onset, feed intake and body weight in female rats. Rats were treated with saline or kisspeptin (100 nmoles per day; intraperitoneal) for 26 days (day 25 to day 50 postnatal) and the day of vaginal opening was marked as day of puberty. Kisspeptin treated rats had delayed pubertal onset and reduced feed intake and body weight. Gonadal GPR54 mRNA was reduced suggesting that chronic high doses of kisspeptin may suppress the reproductive functions possibly by downregulation of GPR54 receptor. However, delay in puberty due to reduction in feed intake and body weight could not be ruled out in this study. Further, our study emphasizes the importance of dosage and duration of kisspeptin administration in the manipulation of reproductive axis. Our study, for the first time, suggests that kisspeptin and its analogues, if proven beneficial, could be used to treat precocious puberty in children. It appears that, though a promising tool for enhancing fertility, kisspeptin acts as a double-edged sword and has to be cautiously used to manipulate reproduction.

• Development and Reproduction
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• v.17 no.1
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• pp.45-53
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• 2013

The action of melatonin within the body of animals is known to be mediated by melatonin receptors. Three different types of melatonin receptors have been identified so far in fish. However, which of these are specifically involved in puberty onset is not known in fish. We cloned and analyzed the sequence of melatonin receptor 1a (mel 1a) gene in Nile tilapia Oreochromis niloticus. In addition, we examined the tissue distribution of gene expressions for three types of receptors, mel 1a, 1b and lc and investigated which of them is involved in the onset of puberty by comparing their expression with that of gonadotropin-releasing hormone receptor I (GnRHr I) gene using quantitative real-time PCR from 1 week post hatch (wph) to 24 wph. The mel 1a gene of Nile tilapia consisted of two exons and one bulky intron between them. Mel 1a gene was found to be highly conserved gene showing high homology with the corresponding genes from different teleost. All three types of melatonin receptor genes were expressed in the brain, eyes and ovary in common. Expression of mel 1a gene was the most abundant and ubiquitous among 3 receptors in the brain, liver, gill, ovary, muscle, eye, heart, intestine, spleen and kidney. Mel 1b and mel 1c genes were, however, expressed in fewer tissues at low level. During the development post hatch, expressions of both mel 1a and GnRHr I genes significantly increased at 13 wph which was close to the putative timing of puberty onset in this species. These results suggest that among three types of receptors mel 1a is most likely associated with the action of melatonin in the onset of puberty in Nile tilapia.

• 대한생식의학회:학술대회논문집
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• 2006.06a
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• pp.171.2-171.2
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• 2006

• Asian-Australasian Journal of Animal Sciences
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• v.15 no.12
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• pp.1714-1718
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• 2002

Twelve prepubertal Karan Fries heifers (15 months, $167.7{\pm}13.5kg$) were divided into two equal groups. Group 1 was fed as per NRC requirements and group 2 was fed 20% more protein than group 1 heifers. The experimental feeding was continued until the onset of puberty in both the groups. Blood samples were collected at fortnightly intervals and analyzed for amino acids using HPLC. Group 1 and 2 heifers required $178.6{\pm}33.8$ and $152.8{\pm}33.2$ days of experimental feeding to exhibit first estrus resulting in total age at puberty as $639.4{\pm}27.3$ and $618.6{\pm}24.6$ days in the two groups respectively. The concentration of total amino acids averaged 4.40 and 4.89 mmol/l and those of non-essential amino acids (NEAA) was 2.32 and 2.49 mmol/l in groups 1 and 2, respectively. The concentration of plasma essential amino acids i.e. histidine, threonine, valine, methionine, isoleucine, leucine and phenylalanine were higher (p<0.01) in group 2 than group 1. Plasma concentration of large neutral amino acids (LNAA) was significantly higher in group 2 (1.28 mmol/l) than in group 1 (1.12 mmol/l). Increased levels of leucine, isoleucine and valine are implicated in increased follicular growth and development in prepubertal heifers and resulted in a 26 day earlier attainment of puberty by 26 days in an experimental period of six months in group 2 heifers. Increased concentrations of aspartate and tyrosine in group 2 heifers might be associated with the release of GnRH from the hypothalamus influencing LH release from anterior pituitary in such animals. It is therefore evident that increased availability of certain amino acids in heifers fed high protein diet might have led to early onset of puberty.