Caprine testicular hypoplasia associated with sexual reversion decreases the expression of insulin-like growth factor II (IGF-II) mRNA in testes

Expression and localization of growth factors and their receptors in the mammalian testis. Part I: Fibroblast growth factors and insulin-like growth factors

It is now well established that normal development and function of testis are mediated by endocrine and paracrine pathways including hormones, growth factors and cytokines as well as by direct cell-to-cell contacts depending on tight, adhering and gap junctions. In the last two decades, several growth factors were identified in the testis of various mammalian species. Growth factors are shown to promote cell proliferation, regulate tissue differentiation, and modulate organogenesis. Interestingly, most of these peptides are expressed not only in the adult mammalian testis during spermatogenesis but also during testicular morphogenesis in prenatal and postnatal life. Our study was launched to provide an overview of the expression, localization, and putative physiological roles of growth factors and their receptors in the mammalian testis. The growth factors considered in this part of our review are fibroblast growth factors and insulin-like growth factors. These factors are found in testicular cells in prenatal, postnatal, and adult animals and are implicated in the regulation of important testicular activities including testicular cord morphogenesis, modulation of testicular hormone secretion and control of spermatogenesis.

Gene expression in the spermatogenically inactive "dark" and maturing "light" testicular tissues of the prepubertal colt

In the testis of the 1.5-year-old horse, spermatogenesis initiates locally in grossly light, central areas that contrast with grossly dark, peripheral areas that are as yet inactive in spermatogenesis. Gene expression was compared between "light" and "dark" tissues of 1.5-year-old horse testes to identify mechanisms important to the initiation of spermatogenesis. Microarrays containing human cDNAs were used to assess expression levels of 9132 genes simultaneously in matched pairs of dark and light testis tissues from 3 prepubertal colts. In all 3 analyses, dysferlin (DYS), down-regulated in ovarian cancer 1 (DOC1), and Golgi apparatus protein 1 (GLG1) genes were preferentially expressed in dark tissues, while outer dense fiber of sperm tails (ODF2) and phosphodiesterase 3B (PDE3B) genes were more highly expressed in light testis tissue (>1.7 balanced difference value, Incyte GEM tools software). Expression levels of 88 additional genes appeared to be different between dark and light tissues in 2 of the 3 microarray analyses. The preferential expression of DYS, DOC1, ODF2, and PDE3B genes in dark or light testis tissues was confirmed on Northern blots and localized to cell types by in situ hybridization. Future studies to determine the role of genes regulated during the initiation of spermatogenesis may aid in elucidating molecular mechanisms during this critical time as well as in identifying new therapies for enhancing male fertility.

Differential expression of IGF components and insulin receptor isoforms in human seminoma versus normal testicular tissue

Insulin-like growth factors (IGF) have mitogenic and antiapoptotic functions, and may be involved in tumor growth. The purpose of the study was to investigate the role of IGF components in seminoma compared to normal testis. Normal testicular tissues from autopsy cases and seminoma from surgery cases were obtained for microarray and real-time reverse transcription polymerase chain reaction (RT-PCR) analysis of IGF-1, IGF-2, IGF receptor type 1 (IGF-R1), IGF-R2, insulin receptor isoforms A (IR-A) and B (IR-B), and IGF-binding proteins (IGFBP) 1-6. IGF-2 was localized by immunohistochemistry. IGFBP-5 protein expression was evaluated by Western blot analysis. mRNA expression in microarray and real-time RT-PCR showed similar tendencies: IGF-1, IGF-R1, IGF-R2, IR-A, and IGFBP-2 were not different in both groups. IGF-2, IR-B, IGFBP-1, IGFBP-4, and IGFBP-6 mRNA were downregulated in seminoma. IGFBP-3 tended to be upregulated in pT1 seminoma, but downregulated in pT2 stages. IGFBP-5 and IGF-2 protein expression correlated with mRNA expression. In conclusion, downregulation of mainly inhibiting IGFBPs may allow a stimulated tumor growth. The downregulated IGF-2 does not seem to be involved in the growth regulation of seminoma. Constantly expressed genes (e.g., IGF-1, IGF-R1, IR-A, and IGFBP-2) may reflect an involvement in spermatogenesis, but may also play a major role in tumor growth as their expression is not downregulated despite the lack of spermatogenesis in tumor tissue.

Large-scale screen for genes involved in gonad development

The vertebrate gonad develops from the intermediate mesoderm as an initially bipotential organ anlage, the genital ridge. In mammals, Sry acts as a genetic switch towards testis development. Sox9 has been shown to act downstream of Sry in testis development, while Dax1 appears to counteract Sry. Few more genes have been implicated in early gonad development. However, the genetic networks controlling early differentiation events in testis and ovary are still far from being understood. In order to provide a broader basis for the molecular analysis of gonad development, high-throughput gene expression analysis was utilized to identify genes specifically expressed in the gonad. In total, among 138 genes isolated which showed tissue specific expression in the embryo, 79 were detected in the developing gonad or sex ducts. Twenty-seven have not been functionally described before, while 40 represent known genes and 12 are putative mouse orthologues. Forty-five of the latter two groups (86%) have not been described previously in the fetal gonad. In addition, 21 of the gonad specific genes showed sex-dimorphic expression suggesting a role in sex determination and/or gonad differentiation. Eighteen of the latter (86%) have not been described previously in the fetal gonad. In total we provide new data on 72 genes which may play a role in gonad or sex duct development and/or sex determination. Thus we have generated a large gene resource for the investigation of these processes, and demonstrate the suitability of high-throughput gene expression screening for the genetic analysis of organogenesis.