Localization of estrogen receptor-alpha and -betamRNA in brain areas controlling sexual behavior in Japanese quail

Two estrogen receptors (ERs), denoted ERalpha and ERbeta, have been identified in humans and various animal species, including the Japanese quail. Estrogens play a key role in sexual differentiation and in activation of sexual behavior in Japanese quail. The distribution of ERalpha in the brain of male and female adult quail has previously been studied using immunohistochemistry, whereas in situ hybridization has been employed to study the distribution of ERbeta mRNA in males only. In this article, we used in situ hybridization to study the distribution of mRNAs for both ERalpha and ERbeta in brain areas controlling sexual behavior of Japanese quail. Our results show that both ERalpha mRNA and ERbeta mRNA are localized in areas important for sexual behavior, such as the preoptic area and associated limbic areas, in both males and females. Moreover, we found differences in distribution of mRNA for the two receptors in these areas. The results of this article support previously reported data and provide novel data on localization of ER mRNAs in adult quail brain of both sexes.     

Identification of the suprachiasmatic nucleus in birds

Circadian rhythms are generated by an internal biological clock. The suprachiasmatic nucleus (SCN) in the hypothalamus is known to be the dominant biological clock regulating circadian rhythms in mammals. In birds, two nuclei, the so-called medial SCN (mSCN) and the visual SCN (vSCN), have both been proposed to be the avian SCN. However, it remains an unsettled question which nuclei are homologous to the mammalian SCN. We have identified circadian clock genes in Japanese quail and demonstrated that these genes are expressed in known circadian oscillators, the pineal and the retina. Here, we report that these clock genes are expressed in the mSCN but not in the vSCN in Japanese quail, Java sparrow, chicken, and pigeon. In addition, mSCN lesions eliminated or disorganized circadian rhythms of locomotor activity under constant dim light, but did not eliminate entrainment under light-dark (LD) cycles in pigeon. However, the lesioned birds became completely arrhythmic even under LD after the pineal and the eye were removed. These results indicate that the mSCN is a circadian oscillator in birds.     

Localization of estrogen receptor‐α and ‐βmRNA in brain areas controlling sexual behavior in Japanese quail

Two estrogen receptors (ERs), denoted ERα and ERβ, have been identified in humans and various animal species, including the Japanese quail. Estrogens play a key role in sexual differentiation and in activation of sexual behavior in Japanese quail. The distribution of ERα in the brain of male and female adult quail has previously been studied using immunohistochemistry, whereas in situ hybridization has been employed to study the distribution of ERβ mRNA in males only. In this article, we used in situ hybridization to study the distribution of mRNAs for both ERα and ERβ in brain areas controlling sexual behavior of Japanese quail. Our results show that both ERα mRNA and ERβ mRNA are localized in areas important for sexual behavior, such as the preoptic area and associated limbic areas, in both males and females. Moreover, we found differences in distribution of mRNA for the two receptors in these areas. The results of this article support previously reported data and provide novel data on localization of ER mRNAs in adult quail brain of both sexes. © 2005 Wiley Periodicals, Inc. J Neurobiol, 2005     

Corticotropin-releasing hormone-immunopositive nerve elements in apposition to chicken gonadotropin-releasing hormone I-containing perikarya in Japanese quail (Coturnix coturnix japonica) brain

The neuroanatomic basis of how stress inhibits reproduction in birds is not understood. To address this question we used double-label immunofluorescence histochemistry to determine whether corticotropin-releasing hormone (CRH)-immunoreactive (ir) neuronal elements contact chicken gonadotropin-releasing hormone I (cGnRH I)-ir somata in brains of Japanese quail. The double-label system used a sheep anti-cGnRH I primary antibody with a secondary antibody conjugated to dichlorotriazinylaminofluorescein dihydrochloride for green fluorescence and a rabbit anti-CRH antibody with a secondary conjugated to Texas Red for red fluorescence. Immunohistochemical (IHC) distribution of both peptides resembled that in previous reports using single-label IHC. In four areas of the quail brain in which CRH nerve fibers and cGnRH I somata co-occurred (bed nucleus commissural pallii, nucleus preopticus medialis, nucleus septalis lateralis and nucleus accumbens), numerous instances were found of CRH-ir nerve fibers or terminals in apposition to cGnRH I cell bodies. These interactions provide a potential neuroanatomic route by which CRH may directly inhibit the activity of cGnRH-I-containing neurons, thereby inhibiting gonadotropin output and halting or slowing the progression of reproductive cycles. It remains to be demonstrated by electron microscopy whether these interactions, which appear abundant by IHC, represent instances of synaptic contact, as has been demonstrated to occur in analogous areas in mammalian species.     

Vasotocin-immunoreactive elements and neuronal typology in the suprachiasmatic nucleus of the chicken and Japanese quail

Summary A Golgi study of the suprachiasmatic nucleus (SCN) of the chicken and Japanese quail revealed in this area a complex neuronal pattern and typology, including specialized dendritic patterns. Immunocytochemical studies provided evidence for the existence of a vasotocinergic system within the SCN, mainly in its rostral portion. Other clusters of immunoreactive elements are located in the lateral and dorsal divisions of this nucleus; they show a different distribution in the chicken and Japanese quail. The present results confirm, in birds, the existence of a morphologically defined SCN, the complex cytoarchitecture of which suggests specialized functions.This study was supported by grants from CNR (83.00447.04, 84.01769.04 and 84.00797.04) and MPI (60%)     

Distribution and metabolism of selenite and selenomethionine in the Japanese quail

Compared to the many studies on the physiological and toxicological effects of selenium (Se) in mammals, avian Se metabolism is still an unexplored topic. Some birds are useful as poultry for human nutrition. Moreover, birds belong to higher trophic levels in the biosphere and thus may play an important role in Se circulation in the ecosystem in the same way as mammals do. In this study, we analyzed the distribution and metabolism of Se in an experimental bird, the Japanese quail, which was fed drinking water containing sodium selenite or selenomethionine (SeMet). The highest concentration of Se was detected in the pancreas, followed by down feathers, liver, and kidneys. SeMet was more efficiently incorporated into the quail than selenite. The specific and preferable distribution of Se to the high molecular weight fraction in the serum of the quail was observed only in the SeMet-ingestion group. As in mammals, selenosugar and trimethylselenonium were the major metabolites in quail excreta. Three unknown Se metabolites were detected by HPLC-ICP-MS. Although part of the metabolic pathway of Se in the Japanese quail fed selenite and SeMet was the same as that observed in mammals, the bird also showed certain avian-specific metabolic process for Se.     

The effects of macrophage-derived cytokines on lipid metabolism in chicken (Gallus domesticus) hepatocytes and adipocytes

1. The effects of avian and mammalian cytokines on avian lipid metabolism were compared using cultured chicken hepatocytes and adipocytes. 2. Conditioned medium from an endotoxin-stimulated chicken macrophage cell line was used as a source of chicken cytokines. Incubation of chicken adipocytes with conditioned medium greatly decreased their lipoprotein lipase activity. 3. Inhibition of lipoprotein lipase synthesis in similar experiments in mammals has been attributed to the effects of TNF-alpha and/or IL-1, but recombinant human TNF-alpha and IL-1 had no effect on lipoprotein lipase activity in chicken adipocytes. 4. Conditioned medium from chicken macrophages produced a 2-fold increase in lipogenesis in chicken adipocytes but had no effect on lipogenesis in chicken hepatocytes. 5. The results point to major differences between mammals and birds in the way that lipid metabolism responds to cytokines and provide further evidence that mammalian cytokines are ineffective in birds.     

Evidence for activation of Amh gene expression by steroidogenic factor 1

The anti-Müllerian hormone gene (Amh) is responsible for regression in males of the Müllerian ducts. The molecular mechanism of regulation of chicken Amh expression is poorly understood. To investigate the regulation of chicken Amh expression, we have cloned Amh cDNAs from quail and duck as well as the promoter regions of the gene from chicken, quail, and duck. The expression patterns of Amh during embryonic development in these three species were found to be similar, suggesting that the regulatory mechanisms of Amh expression are conserved. The sequence of the proximal promoter of Amh contains a putative binding site for steroidogenic factor 1 (SF1), the protein product of which can up-regulate Amh in mammals. We showed here that SF1 is able to activate the chicken Amh promoter and binds to its putative SF1 binding site. These results suggest that SF1 plays a role in regulation of Amh expression in avian species.     

Avian pallial circuits and cognition: A comparison to mammals

Cognitive functions are similar in birds and mammals. So, are therefore pallial cellular circuits and neuronal computations also alike? In search of answers, we move in from bird’s pallial connectomes, to cortex-like sensory canonical circuits and connections, to forebrain micro-circuitries and finally to the avian “prefrontal” area. This voyage from macro- to micro-scale networks and areas reveals that both birds and mammals evolved similar neural and computational properties in either convergent or parallel manner, based upon circuitries inherited from common ancestry. Thus, these two vertebrate classes evolved separately within 315 million years with highly similar pallial architectures that produce comparable cognitive functions.     

Male-specific cell migration into the developing gonad is a conserved process involving PDGF signalling

Male-specific migration of cells from the mesonephric kidney into the embryonic gonad is required for testis formation in the mouse. It is unknown, however, whether this process is specific to the mouse embryo or whether it is a fundamental characteristic of testis formation in other vertebrates. The signalling molecule/s underlying the process are also unclear. It has previously been speculated that male-specific cell migration might be limited to mammals. Here, we report that male-specific cell migration is conserved between mammals (mouse) and birds (quail-chicken) and that it involves proper PDGF signalling in both groups. Interspecific co-cultures of embryonic quail mesonephric kidneys together with embryonic chicken gonads showed that quail cells migrated specifically into male chicken gonads at the time of sexual differentiation. The migration process is therefore conserved in birds. Furthermore, this migration involves a conserved signalling pathway/s. When GFP-labelled embryonic mouse mesonephric kidneys were cultured together with embryonic chicken gonads, GFP+ mouse cells migrated specifically into male chicken gonads and not female gonads. The immigrating mouse cells contributed to the interstitial cell population of the developing chicken testis, with most cells expressing the endothelial cell marker, PECAM. The signalling molecule/s released from the embryonic male chicken gonad is therefore recognised by both embryonic quail and mouse mesonephric cells. A candidate signalling molecule mediating the male-specific cell migration is PDGF. We found that PDGF-A and PDGF receptor-alpha are both up-regulated male-specifically in embryonic chicken and mouse gonads. PDGF signalling involves the phosphotidylinositol 3-kinase (PIK3) pathway, an intracellular pathway proposed to be important for mesonephric cell migration in the mammalian gonad. We found that a component of this pathway, PI3KC2alpha, is expressed male-specifically in developing embryonic chicken gonads at the time of sexual differentiation. Treatment of organ cultures with the selective PDGF receptor signalling inhibitor, AG1296 (tyrphostin), blocked or impaired mesonephric cell migration in both the mammalian and avian systems. Taken together, these studies indicate that a key cellular event in gonadal sex differentiation is conserved among higher vertebrates, that it involves PDGF signalling, and that in mammals is an indirect effect of Sry expression.     

The Avian XPR1 Gammaretrovirus Receptor Is under Positive Selection and Is Disabled in Bird Species in Contact with Virus-Infected Wild Mice

Xenotropic mouse leukemia viruses (X-MLVs) are broadly infectious for mammals except most of the classical strains of laboratory mice. These gammaretroviruses rely on the XPR1 receptor for entry, and the unique resistance of laboratory mice is due to two mutations in different putative XPR1 extracellular loops. Cells from avian species differ in susceptibility to X-MLVs, and 2 replacement mutations in the virus-resistant chicken XPR1 (K496Q and Q579E) distinguish it from the more permissive duck and quail receptors. These substitutions align with the two mutations that disable the laboratory mouse XPR1. Mutagenesis of the chicken and duck genes confirms that residues at both sites are critical for virus entry. Among 32 avian species, the 2 disabling XPR1 mutations are found together only in the chicken, an omnivorous, ground-dwelling fowl that was domesticated in India and/or Southeast Asia, which is also where X-MLV-infected house mice evolved. The receptor-disabling mutations are also present separately in 5 additional fowl and raptor species, all of which are native to areas of Asia populated by the virus-infected subspecies Mus musculus castaneus. Phylogenetic analysis showed that the avian XPR1 gene is under positive selection at sites implicated in receptor function, suggesting a defensive role for XPR1 in the avian lineage. Contact between bird species and virus-infected mice may thus have favored selection of mouse virus-resistant receptor orthologs in the birds, and our data suggest that similar receptor-disabling mutations were fixed in mammalian and avian species exposed to similar virus challenges.     

Establishment of inbred strains of chicken and Japanese quail and their potential as animal models.

We started establishing inbred strains of chicken and Japanese quail in 1970. In class Aves, full sib mating is highly difficult due to inbreeding depression. In the chicken, we attempted to establish some inbred strains in three breeds, Black Minorca, White Leghorn and Fayoumi by fixing all the characters that differentiate individuals homozygously. In this paper, we describe some marker genes and characters fixed in the inbred strains of chicken and Japanese quail as well as a calculation of a putative coefficient of inbreeding in 8 chicken inbred strains using band sharing values detected by AFLP analysis. We established generalized glycogenosis type II quail, myotonic dystrophy quail, neurofilament deficient quail, visually impaired chicken, double oviduct chicken with partial kidney deficiency, chicken showing spontaneous lymphocytic thyroiditis with feathered amelanosis, and chicken with a hereditary nervous disorder. The processes of establishment and characteristics of these animal models are described with some interesting information obtained from these animal models. In generalized glycogenosis type II quail, the results of enzyme replacement therapy and gene therapy are described.     

Molecular cloning of growth hormone secretagogue-receptor and effect of quail ghrelin on gastrointestinal motility in Japanese quail

We identified a growth hormone secretagogue-receptor (GHS-R) for ghrelin (GRLN) in the Japanese quail, and examined relationship between its receptor distribution and the effects of ghrelin on the gastrointestinal tract of the quail. GHS-R expression and GRLN-induced response were also investigated in the chicken and compared with quail. Several types of GHS-R, namely GHS-R1a-L, GHS-R1a-S, GHS-R1aV, GHS-R1b, GHS-R1bV and GHS-R1tv-like receptor, were identified in quail cerebellum cDNA. Amino acid sequence of quail GHS-R1a-L was 98% identical to that of chicken GHS-R1a. GHS-R1a mRNA was expressed heterogeneously in the quail gastrointestinal tract with a high expression level in the colon, moderate levels in the esophagus and crop, and low levels in the proventriculus, gizzard and small intestine. The region-specific expression pattern was almost the same as that in the chicken. Chicken and quail GRLN caused contraction in the crop, proventriculus and colon of both the quail and chicken, whereas the small intestine was less sensitive. However, the contractile efficacy was more potent in the chicken than in the quail. Chicken motilin (MTL), another gut peptide, structurally resemble to GRLN, caused marked contraction in the small intestine of both the quail and chicken, and the region-specific effect of MTL was opposite to that of GRLN. In conclusion, GRLN mainly induces the contractile responses of the upper and lower gastrointestinal tract and MTL stimulates motility of the middle intestine in both the quail and chicken. Regions in which GRLN acts were consistent with the distribution of GHS-R1a mRNA, but the contractile efficacy was different in the quail and chicken. These results suggest a species-specific contribution of GRLN in the regulation of avian gastrointestinal contractility.     

Molecular and functional characterization of a vasotocin-sensitive aquaporin water channel in quail kidney

Both mammals and birds can concentrate urine hyperosmotic to plasma via a countercurrent multiplier mechanism, although evolutionary lines leading to mammals and birds diverged at an early stage of tetrapod evolution. We reported earlier (Nishimura H, Koseki C, and Patel TB. Am J Physiol Regul Integr Comp Physiol 271: R1535-R1543, 1996) that arginine vasotocin (AVT; avian antidiuretic hormone) increases diffusional water permeability in the isolated, perfused medullary collecting duct (CD) of the quail kidney. In the present study, we have identified an aquaporin (AQP) 2 homolog water channel in the medullary cones of Japanese quail, Coturnix coturnix (qAQP2), by RT-PCR-based cloning techniques. A full-length cDNA contains an 822-bp open reading frame that encodes a 274-amino acid sequence with 75.5% identity to rat AQP2. The qAQP2 has six transmembrane domains, two asparagine-proline-alanine (NPA) sequences, and putative N-glycosylation (asparagine-124) and phosphorylation sites (serine-257) for cAMP-dependent protein kinase. qAQP2 is expressed in the membrane of Xenopus laevis oocytes and significantly increased its osmotic water permeability (P(f)), inhibitable (P < 0.01) by mercury chloride. qAQP2 mRNA (RT-PCR) was detected in the kidney; medullary mRNA levels were higher than cortical levels. qAQP2 protein that binds to rabbit anti-rat AQP2 antibody is present in the apical/subapical regions of both cortical and medullary CDs from normally hydrated quail, and the intensity of staining increased only in the medullary CDs after water deprivation or AVT treatment. The relative density of the approximately 29-kDa protein band detected by immunoblot from the medullary cones was modestly higher in water-deprived/AVT-treated quail. The results suggest that 1) medullary CDs of quail kidneys express a mercury-sensitive functioning qAQP2 water channel, and 2) qAQP2 is at least partly regulated by an AVT-dependent mechanism. This is the first clear identification of AQP2 homolog in nonmammalian vertebrates.