Mll5 is required for normal spermatogenesis.

BACKGROUND: Mll5 is currently a member of the Mll family of SET domain histone methyltransferase proteins but studies have also showed that it could be part of the SET3 branch of proteins. Recently, constitutive knock out animal studies have shown that Mll5 is required for proper haematopoietic stem cell differentiation, and loss of Mll5 results in synthetic lethality for genome de-methylation. Mll5 deficient male mice are infertile and here we analyse the consequences of Mll5 deficiency for spermatogenesis. METHODOLOGY/PRINCIPAL FINDINGS: Mll5 deficient male mice, but not female mice, are infertile. Here we show using RNA in-situ hybridization that Mll5 is expressed in the germ cells of the testes of wild type mice. Consistent with the expression of Mll5, we demonstrate by electron microscopy, video microscopy and in vitro fertilisation techniques that Mll5 deficient mice have defects in terminal maturation and packaging of sperm. The defects seen include detachment of the acrosomal cap and impaired excess cytoplasm removal. Functional tests of sperm motility show a lack of progressive motility of spermatozoa from Mll5 deficient animals. None of these defects could be rescued by in vitro fertilization. Using microarray analysis we show that transcripts implicated in spermatogenesis are dysregulated. CONCLUSIONS/SIGNIFICANCE: Our data demonstrate a clear role of Mll5 in mammalian spermatogenesis at the level of terminal differentiation providing further support for its classification in the SET3 branch of proteins. Moreover, this study identifies Tlk2, Utx, Gpr64, Sult4a1, Rap2ip, Vstm2 and HoxA10 as possible Mll5 targets that together may account for the observed spermatozoa maturation defects.

Kisspeptin neurons co-express met-enkephalin and galanin in the rostral periventricular region of the female mouse hypothalamus.

It is now well established that the kisspeptin neurons of the hypothalamus play a key role in regulating the activity of gonadotropin-releasing hormone (GnRH) neurons. The population of kisspeptin neurons residing in the rostral periventricular region of the third ventricle (RP3V), encompassing the anteroventral periventricular (AVPV) and periventricular preoptic nuclei (PVpo), are implicated in the generation of the preovulatory GnRH surge mechanism and puberty onset in female rodents. The present study examined whether these kisspeptin neurons may express other neuropeptides in the adult female mouse. Initially, the distribution of galanin, neurotensin, met-enkephalin (mENK), and cholecystokinin (CCK)-immunoreactive cells was determined within the RP3V of colchicine-treated mice. Subsequent experiments, using a new kisspeptin-10 antibody raised in sheep, examined the relationship of these neuropeptides to kisspeptin neurons. No evidence was found for expression of neurotensin or CCK by RP3V kisspeptin neurons, but subpopulations of kisspeptin neurons were observed to express galanin and mENK. Dual-labeled RP3V kisspeptin/galanin cells represented 7% of all kisspeptin and 21% of all galanin neurons whereas dual-labeled kisspeptin/mENK cells represented 28-38% of kisspeptin neurons and 58-68% of the mENK population, depending on location within the AVPV or PVpo. Kisspeptin neurons in the arcuate nucleus were also found to express galanin but not mENK. These observations indicate that, like the kisspeptin population of the arcuate nucleus, kisspeptin neurons in the RP3V also co-express a range of neuropeptides. This pattern of co-expression should greatly increase the dynamic range with which kisspeptin neurons can modulate the activity of their afferent neurons.

Function-related structural plasticity of the GnRH system: a role for neuronal-glial-endothelial interactions.

As the final common pathway for the central control of gonadotropin secretion, GnRH neurons are subjected to numerous regulatory homeostatic and external factors to achieve levels of fertility appropriate to the organism. The GnRH system thus provides an excellent model in which to investigate the complex relationships between neurosecretion, morphological plasticity and the expression of a physiological function. Throughout the reproductive cycle beginning from postnatal sexual development and the onset of puberty to reproductive senescence, and even within the ovarian cycle itself, all levels of the GnRH system undergo morphological plasticity. This structural plasticity within the GnRH system appears crucial to the timely control of reproductive competence within the individual, and as such must have coordinated actions of multiple signals secreted from glial cells, endothelial cells, and GnRH neurons. Thus, the GnRH system must be viewed as a complete neuro-glial-vascular unit that works in concert to maintain the reproductive axis.

Distribution and postnatal development of Gpr54 gene expression in mouse brain and gonadotropin-releasing hormone neurons.

Kisspeptin and G protein-coupled receptor 54 (GPR54) are now acknowledged to play essential roles in the neural regulation of fertility. Using a transgenic Gpr54 LacZ knock-in mouse model, this study aimed to provide 1) a detailed map of cells expressing Gpr54 in the mouse brain and 2) an analysis of Gpr54 expression in GnRH neurons across postnatal development. The highest density of Gpr54-expressing cells in the mouse central nervous system was found in the dentate gyrus of the hippocampus beginning on postnatal d 6 (P6). Abundant Gpr54 expression was also noted in the septum, rostral preoptic area (rPOA), anteroventral nucleus of the thalamus, posterior hypothalamus, periaqueductal grey, supramammillary and pontine nuclei, and dorsal cochlear nucleus. No Gpr54 expression was detected in the arcuate and rostral periventricular nuclei of the hypothalamus. Dual-labeling experiments showed that essentially all Gpr54-expressing cells in the rPOA were GnRH neurons. Analyses of mice at birth, P1, P5, P20, and P30 and as adults revealed a gradual increase in the percentage of GnRH neurons expressing Gpr54 from approximately 40% at birth through to approximately 70% from P20 onward. Whereas GnRH neurons located in the septum displayed a consistent increase across this time, GnRH neurons in the rPOA showed a sharp reduction in Gpr54 expression after birth (to approximately 10% at P5) before increasing to the 70% expression levels by P20. Together these findings provide an anatomical basis for the exploration of Gpr54 actions outside the reproductive axis and reveal a complex temporal and spatial pattern of Gpr54 gene expression in developing GnRH neurons.