Pituitary-Specific Overexpression of Porcine Follicle-Stimulating Hormone Leads to Improvement of Female Fecundity in BAC Transgenic Mice

Mingjun Bi,Hengxi Wei,Jing Wang,Yunping Dai,Fei Chang,Ning Li,Yaofeng Zhao,Jia Tong,Mingxing Chu,Marlon R Schneider

doi:10.1371/journal.pone.0042335

Abstract

Follicle-stimulating hormone (FSH) is a pituitary glycoprotein that, together with luteinizing hormone, plays a crucial role in ovarian folliculogenesis and female fertility. We previously found that FSH beta is a major gene controlling high prolificacy of Chinese Erhualian pigs. To directly study the biological effects on reproductive function of porcine FSH (pFSH) for polyovulatory species, we generated a novel gain-of-function mouse model using a bacterial artificial chromosome (BAC) system to jointly introduce 92 kb and 165 kb genomic fragments comprising the pFSH α- and β-subunit genes. These directed the physiological expression of pFSH with the same temporal and spatial pattern as endogenous FSH in female transgenic (TG) mice. Serum levels of biologically active pFSH heterodimers in independent TG lines ranged from 6.36 to 19.83 IU/L. High basal pFSH activity led to a significant reduction of serum LH and testosterone levels in TG females compared to wild-type (WT) littermates, yet endogenous FSH and estradiol levels were significantly elevated. Interestingly, ovarian histology showed that the number of corpora lutea was significantly higher at 14 and 28 weeks of age in TG females and breeding curves revealed that mean litter sizes of TG females were obviously larger than for WT littermates before 52 weeks of age. These findings indicate that pituitary-specific overexpression of pFSH within physiological boundaries can increase ovulation rate and litter size, but it does not cause reproductive defects. Therefore, our TG mouse model provides exciting insights for investigating the actions of pFSH in vivo.

Highlights

The glycoprotein hormone superfamily includes follicle-stimulating hormone (FSH), luteinizing hormone (LH), and thyroidstimulating hormone (TSH), as well as placental chorionic gonadotropin (CG) which is present only in primates and horse
Expression was only observed in pituitary; no ectopic expression was observed in the other tissues examined. These results indicate that the major regulatory elements required for tissue-specific expression of pFSHa and pFSHb are present within the BAC412H8 and BAC183O11 transgenes, respectively
bacterial artificial chromosome (BAC) transgenesis represents a major breakthrough in the functional generation of TG animals [34] and has been applied to devise new animal models of human genetic diseases, to study gene function during development, and to produce recombinant proteins in the mammary glands of transgenic animals [35,36,37,38,39,40]

Summary

Introduction

The glycoprotein hormone superfamily includes follicle-stimulating hormone (FSH), luteinizing hormone (LH), and thyroidstimulating hormone (TSH), as well as placental chorionic gonadotropin (CG) which is present only in primates and horse. Transgenic (TG) mice harboring the human FSH two subunit genes have been used previously to explore the role of FSH in reproductive function, and these animals have provided important information about the pathological effects of FSH levels that exceed normal physiological boundaries [7,8,9]. These models are useful for studying human pathologies and for mimicking reproductive diseases. To evaluate the physiological effects of normal expression profile of porcine FSH (pFSH) for polyovulatory species in vivo, we took advantage of large-fragment TG strategies to establish TG mice

Methods

Results

Conclusion