Biomedical subjects

Serge Nef

Publications and source records attributed to Serge Nef.

14 recordsLinked to original sources

PubMed2025

Ovarian development is driven by early spatiotemporal priming of the coelomic epithelium.

Ovarian organogenesis requires the coordinated specification of supporting and steroidogenic cell lineages from multipotent coelomic epithelium (CE) progenitors. A longstanding question is whether the CE contains transcriptionally distinct, spatially organized progenitor subpopulations with predetermined lineage biases, or whether specification into supporting and steroidogenic lineages occurs only after delamination and integration into the bipotential gonad. The developmental origins of granulosa cells and the emergence of ovarian steroidogenic/stromal progenitors (SPs) also remain poorly defined. Here, we show that CE cells covering the fetal mouse ovary are transcriptionally heterogeneous and spatially organized into subdomains already primed toward supporting or steroidogenic fates. CE priming is dynamic, with transient coexistence of supporting- and steroidogenic-biased CE progenitors before resolving into a predominantly supporting-biased CE. Local delamination of these primed cells seeds intragonadal niches where pre-granulosa cells and SPs mirror the spatio-temporal arrangements of CE-primed progenitors. We further demonstrate a dual origin for the supporting lineage, with granulosa cells deriving from both the CE and supporting-like cells (SLCs). In parallel, we show that SPs arise from steroidogenic-primed CE cells, expand to represent 52% of ovarian somatic cells at birth, persist into adulthood and contribute to both theca and steroidogenic stromal cells. Together, these findings reveal transcriptionally and spatially distinct CE subpopulations that shape somatic lineage emergence with important implications for ovarian pathophysiology.

Ovarian development↗

PubMed2007

Genetic programs that regulate testicular and ovarian development.

The gonadal primordium is the only tissue in mammals that has two divergent developmental fates leading ultimately to the formation of either a testis or an ovary. The goal of this review is to summarize the major characteristics of the male and female transcriptional programs triggered in the developing mouse gonads during the critical time window of sex determination. Expression profiling studies reveal that both male and female genetic programs are initiated as early as embryonic day (E) 11.5. By E13.5, more than 1000 genes are overexpressed either in developing ovaries or testes. A large fraction of these have so far no known roles during gonadal differentiation, yet interestingly some of their human orthologues map to chromosomal loci associated with sexual disorders. Identifying the functional roles for these candidate genes will improve our understanding of sex determination and provide new insights into the causes of gonadal dysgenesis and reproductive disorders.

Animals↗

PubMed2006

Brain-derived neurotrophic factor conditional knockouts show gender differences in depression-related behaviors.

BACKGROUND: Indirect evidence suggests that loss of brain-derived neurotrophic factor (BDNF) from forebrain regions contributes to an individual's vulnerability for depression, whereas upregulation of BDNF in these regions is suggested to mediate the therapeutic effect of antidepressants. METHODS: We have tested this hypothesis by generating two independent lines of conditional BDNF knockout mice in which the BDNF gene is deleted selectively in forebrain. RESULTS: We show that male conditional knockouts exhibit hyperactivity but normal depression-related behaviors. In contrast, female conditional knockouts display normal locomotor activity but a striking increase in depression-like behavior. We also demonstrate that loss of BDNF in both male and female mice attenuates the actions of the antidepressant desipramine in the forced swim test. CONCLUSIONS: These gender differences in depression-related behaviors in BDNF conditional knockout mice provide direct evidence for a role of BDNF in depression. The results also support the view that forebrain BDNF may be essential in mediating antidepressant efficacy.

Alleles↗

PubMed2006

Expression of serpinb6 serpins in germ and somatic cells of mouse gonads.

The serpin superfamily of serine protease inhibitors is implicated in the regulation of numerous physiological processes. In mice, Spi3/Serpinb6 has a broad tissue distribution. We have investigated the expression of Serpinb6 family members in embryonic and adult gonads. In male and female mice, Spi3/Serpinb6 and NK13/Serpinb6b were expressed in developing gonads and in both somatic and germ cells of adult gonads. By contrast, gonadal expression of Spi3C/Serpinb6c was sexually dimorphic and restricted to male germ cells and female somatic cells. These observations raise the question of the possible role(s) of the Serpinb6 family members in gonad development, gametogenesis, and/or fertilization.

Animals↗

PubMed2005

Gene expression during sex determination reveals a robust female genetic program at the onset of ovarian development.

The primary event in mammalian sexual development is the differentiation of the bipotential gonads into either testes or ovaries. Our understanding of the molecular pathways specifying gonadal differentiation is still incomplete. To identify the initial molecular changes accompanying gonadal differentiation in mice, we have performed a large-scale transcriptional analysis of XX and XY Sf1-positive gonadal cells during sex determination. In both male and female genital ridges, a robust genetic program is initiated pre-dating the first morphological changes of the differentiating gonads. Between E10.5 and E13.5, 2306 genes were expressed in a sex-specific manner in the somatic compartment of the gonads; 1223 were overexpressed in XX embryos and 1083 in XY embryos. Although sexually dimorphic genes were scattered throughout the mouse genome, we identified chromosomal regions hosting clusters of genes displaying similar expression profiles. The cyclin-dependent kinase inhibitors Cdkn1a and Cdkn1c are overexpressed in XX gonads at E11.5 and E12.5, suggesting that the increased proliferation of XY gonads relative to XX gonads may result from the overexpression of cell cycle inhibitors in the developing ovaries. These studies define the major characteristics of testicular and ovarian transcriptional programs and reveal the richness of signaling processes in differentiation of the bipotential gonads into testes and ovaries.

Animals↗

PubMed2005

Prostaglandin D2 induces nuclear import of the sex-determining factor SOX9 via its cAMP-PKA phosphorylation.

During mammalian gonadal development, nuclear import/export of the transcription factor SOX9 is a critical step of the Sry-initiated testis-determining cascade. In this study, we identify a molecular mechanism contributing to the SOX9 nuclear translocation in NT2/D1 cells, which is mediated by the prostaglandin D2 (PGD2) signalling pathway via stimulation of its adenylcyclase-coupled DP1 receptor. We find that activation of cAMP-dependent protein kinase A (PKA) induces phosphorylation of SOX9 on its two S64 and S181 PKA sites, and its nuclear localization by enhancing SOX9 binding to the nucleocytoplasmic transport protein importin beta. Moreover, in embryonic gonads, we detect a male-specific prostaglandin D synthase expression and an active PGD2 signal at the time and place of SOX9 expression. We thus propose a new step in the sex-determining cascade where PGD2 acts as an autocrine factor inducing SOX9 nuclear translocation and subsequent Sertoli cell differentiation.

Animals↗

PubMed2005

TrkB has a cell-autonomous role in the establishment of hippocampal Schaffer collateral synapses.

Neurotrophin signaling has been implicated in the processes of synapse formation and plasticity. To gain additional insight into the mechanism of BDNF and TrkB influence on synapse formation and synaptic plasticity, we generated a conditional knock-out for TrkB using the cre/loxp system. Using three different cre-expressing transgenic mice, three unique spatial and temporal configurations of TrkB deletion were obtained with regard to the hippocampal Schaffer collateral synapse. We compare synapse formation in mutants in which TrkB is ablated either in presynaptic or in both presynaptic and postsynaptic cells at early developmental or postdevelopmental time points. Our results indicate a requirement for TrkB at both the presynaptic and postsynaptic sites during development. In the absence of TrkB, synapse numbers were significantly reduced. In vivo ablation of TrkB after synapse formation did not affect synapse numbers. In primary hippocampal cultures, deletion of TrkB in only the postsynaptic cell, before synapse formation, also resulted in deficits of synapse formation. We conclude that TrkB signaling has a cell-autonomous role required for normal development of both presynaptic and postsynaptic components of the Schaffer collateral synapse.

Animals↗

PubMed2005

Hormonal regulation of male reproductive tract development.

We have employed gene knockout technology in mice to probe gene function in various stages of mouse male sexual differentiation. Insulin-like factor (Insl3) is prominently expressed in Leydig cells. Mutation of this gene leads to fully penetrant cryptorchidism. Single mutation in each of the three known insulin family receptor tyrosine kinases alone has limited effects on sexual differentiation; however, compound mutations result in formation of ovotestes, and triple mutations cause male-to-female sexual reversal. The implications of our mouse models are discussed.

Animals↗

PubMed2004

Conditional deletion of TrkB but not BDNF prevents epileptogenesis in the kindling model.

Epileptogenesis is the process whereby a normal brain becomes epileptic. We hypothesized that the neurotrophin brain-derived neurotrophic factor (BDNF) activates its receptor, TrkB, in the hippocampus during epileptogenesis and that BDNF-mediated activation of TrkB is required for epileptogenesis. We tested these hypotheses in Synapsin-Cre conditional BDNF(-/-) and TrkB(-/-) mice using the kindling model. Despite marked reductions of BDNF expression, only a modest impairment of epileptogenesis and increased hippocampal TrkB activation were detected in BDNF(-/-) mice. In contrast, reductions of electrophysiological measures and no behavioral evidence of epileptogenesis were detected in TrkB(-/-) mice. Importantly, TrkB(-/-) mice exhibited behavioral endpoints of epileptogenesis, tonic-clonic seizures. Whereas TrkB can be activated, and epileptogenesis develops in BDNF(-/-) mice, the plasticity of epileptogenesis is eliminated in TrkB(-/-) mice. Its requirement for epileptogenesis in kindling implicates TrkB and downstream signaling pathways as attractive molecular targets for drugs for preventing epilepsy.

Animals↗

PubMed2004

Induction of enhanced green fluorescent protein expression in response to lesions in the nervous system.

We have generated a mouse strain carrying a transgene driven by a strong and ubiquitous promoter (human cytomegalovirus hCMV/beta-actin) and containing an enhanced green fluorescent protein (eGFP) coding sequence upstream of the 3' untranslated region (3'UTR) of tissue-type plasminogen activator (t-PA) mRNA. The 3'UTR of t-PA mRNA is known to be involved in the reversible deadenylation and translational repression of transcripts in mouse oocytes. hCMV/beta-actin-eGFP-3'UTR t-PA transgenic mice express eGFP mRNA in all brain structures analyzed but lack eGFP fluorescence, with the exception of blood vessels, choroid plexus, and Purkinje cells. Taking advantage of these features, we tested whether certain pathological conditions, in particular injuries of the nervous system, might trigger eGFP fluorescence in traumatized cells or neurons. From this perspective, we analyzed eGFP mRNA expression and eGFP fluorescence in experimental models of nervous system lesions, such as motoneuron axotomy and cerebral stroke induced by middle cerebral artery occlusion. We found an increase in eGFP fluorescence in specific brain areas in cells suffering or reacting to these injuries. This increased fluorescence is correlated with an increased transcription of eGFP in lesioned cells, presumably enhanced by a release of the translational silencing mediated by the 3'UTR region of the t-PA mRNA. This transgenic mouse model may prove useful to study the development of neurodegenerative lesions.

Animals↗

PubMed2003

Testis determination requires insulin receptor family function in mice.

In mice, gonads are formed shortly before embryonic day 10.5 by the thickening of the mesonephros and consist of somatic cells and migratory primordial germ cells. The male sex-determining process is set in motion by the sex-determining region of the Y chromosome (Sry), which triggers differentiation of the Sertoli cell lineage. In turn, Sertoli cells function as organizing centres and direct differentiation of the testis. In the absence of Sry expression, neither XX nor XY gonads develop testes, and alterations in Sry expression are often associated with abnormal sexual differentiation. The molecular signalling mechanisms by which Sry specifies the male pathway and models the undifferentiated gonad are unknown. Here we show that the insulin receptor tyrosine kinase family, comprising Ir, Igf1r and Irr, is required for the appearance of male gonads and thus for male sexual differentiation. XY mice that are mutant for all three receptors develop ovaries and show a completely female phenotype. Reduced expression of both Sry and the early testis-specific marker Sox9 indicates that the insulin signalling pathway is required for male sex determination.

Animals↗

PubMed2003

Emotions are building up in the field of extracellular proteolysis.

Activity-dependent remodeling of neural connections might require localized extracellular proteolysis. The tissue-type plasminogen activator (tPA)-plasmin proteolytic system is expressed in different regions of the central nervous system, in the context of a variety of physiological and pathological processes. Accumulating evidence regarding the expression and role of tPA and its inhibitors suggests that extracellular proteolysis is a key player in the biology of memory, emotions and neurodegeneration.

Animals↗

PubMed2002

Effects of orchiopexy on congenitally cryptorchid insulin-3 knockout mice.

PURPOSE: Insulin-3 (Insl3) knockout mice exhibit isolated, bilateral, high intra-abdominal cryptorchidism. If left in this position until adulthood, these testes will deteriorate to the Sertoli-cell-only state, leading to infertility in 100%. We examined the effect of orchiopexy in this genetically engineered animal model. MATERIALS AND METHODS: A total of 160 testes from 80 male offspring of Insl3 F crosses underwent either no orchiopexy (29 testes), sham surgery (25 testes), 1-stage Fowler-Stephens scrotal orchiopexy (57 testes) or primary orchiopexy into a low abdominal, subcutaneous pouch (49 testes). A group of postoperative mice underwent fertility testing 3 months postoperatively. At 6 to 9 months postoperatively the testes were harvested and histologically analyzed. RESULTS: Testes were atrophic in 100% (25 of 25) of the sham group, 91% (52 of 57) of the Fowler-Stephens orchiopexy group and 33% (16 of 49) of the subcutaneous pouch group (testis weight less than 50 mg.). Fertility testing was done in 30 mice (sham 5, Fowler-Stephens orchiopexy 17 and subcutaneous pouch 8). Infertility was secondary to bilateral testicular atrophy (sham 5 of 5, Fowler-Stephens orchiopexy 13 of 17), spermatogenic maturation arrest (subcutaneous pouch 8 of 8) and ductal obstruction [normal spermatogenesis with epididymis devoid of sperm] (Fowler-Stephens orchiopexy 2 of 17). Fertility with normal spermatogenesis was observed in 2 of 17 Fowler-Stephens orchiopexy mice, both of which were Insl3 knockout mice. CONCLUSIONS: Intrascrotal orchiopexy can rescue these congenitally cryptorchid Insl3 knockout testes from their intra-abdominal fate of Sertoli-cell-only and lead to fertility. The results suggest that orchiopexy has a crucial and central role in preservation of spermatogenesis.

Animals↗

PubMed2002

The insulin-3 gene: lack of a genetic basis for human cryptorchidism.

PURPOSE: The etiology of cryptorchidism appears to be multifactorial and related to hormonal and mechanical factors. Recently, the insulin-3 gene (INSL3) was noted to have a role in mouse gubernacular development and testicular descent. Knockout male mice for the INSL3 gene show isolated bilateral cryptorchidism. This phenotype suggests that INSL3 may have a role in the development of human cryptorchidism. Using single strand conformational polymorphism analysis we detected mutations of the INSL3 gene in boys with cryptorchidism. MATERIALS AND METHODS: Genomic DNA from 118 boys with cryptorchidism and 48 normal controls were obtained from 3 institutions. Using polymerase chain reaction with INSL3 sequence specific primers DNA fragments were analyzed using single strand conformational polymorphism reactions. Samples with band shifts were re-amplified and sequenced to detect mutations. RESULTS: A single base substitution (G greater than A) causing an amino acid change (missense mutation) was identified in 27 of 118 cryptorchid (23%) samples and 12 of 48 normal (25%) samples. Two other base substitutions did not produce alterations in the amino acid sequence (silent mutations). CONCLUSIONS: Although a common polymorphism was detected in the INSL3 gene, no specific mutations were detected in a large population of individuals with cryptorchidism. Therefore, mutations in the coding region of the INSL3 gene are not a common cause of human cryptorchidism.

Child↗