C Response to hermaphrodite pheromones

The existence of hermaphrodite-produced pheromone(s) detected by males has long been postulated but has remained elusive. Recently, several groups have demonstrated that males can recognize culture medium conditioned by hermaphrodites (Simon and Sternberg, 2002 J. White and E. M. Jorgensen, personal communication K. L. Chow, personal communication A. Barrios and S. W. Emmons, personal communication) or by females from other Caenor-habditis species (Chasnov et al., 2007). Depending on the assay...

Sexual Differentiation Of Vocal Control Areas In Adulthood

Sex Differentiation

Hormone-driven behavioral differentiation in adulthood is generally thought to be due to transient hormone-induced alterations of vocal area size that, in turn, is explained by changes of neuron numbers, neuronal size, neuron spacing, or of the size of terminal fields of projection neurons (Nottebohm, 1980, 1981 Nottebohm et al., 1986 but Gahr, 1990, 1997). Differences in the relative importance of these mechanisms for volume changes of different vocal areas are obvious for example, RA does not...

Homosexual Brains Are Different

Neuropsychological studies have reported differences in performance on tasks that show sex differences, such as spatial processing (Rahman and Wilson, 2003), which may indicate differences in relevant neural structures. Neuroanatomical differences have been reported for three brain regions based on sexual orientation in males the arginine vasopressin neuronal population of the suprachiasmatic nucleus (Swaab et al., 1997), the third interstitial nucleus of the anterior hypothalamus (LeVay,...

Molecular Biology Of Pheromone Reception

In mice, pheromones are detected by two anatomically distinct olfactory systems the main olfactory system and the vomeronasal (or accessory olfactory) system. The olfactory neurons express a repertoire of olfactory receptors (ORs), which is responsible for detecting volatile odorants and pheromones. The vomeronasal sensory epithelium in the VNO can be divided into apical and basal layers, which express V1R- and V2R-type receptors, respectively (Berghard and Buck, 1996 Dulac and Axel, 1995...

Genomic Imprinting Hypothalamic Development And Behavior

The dual action of imprinted genes on the placenta and hypothalamus has both genetically and epigenetically ensured that the female reproductive strategy is strongly biased toward maternalism. Sexual behavior is a rare event in the life of a female rodent and is epitomized by a reflexive lordosis reactive response to the male. Male sexual behavior is very different, being a frequent behavioral preoccupation that involves proactively finding oestrous females and competing aggressively for them...

Parental effects on life history strategies

Variations in life history strategies among individuals within a species are often defined by adaptations to environmental conditions prevailing during early development, and reflect the remarkable capacity for phenotypic plasticity. Research in evolutionary biology reveals so-called parental effects (Agrawal, 2001 Cameron et al., 2005 Groothuis et al., 2005 Mousseau and Fox, 1998 Qvarnstrom and Price, 2001 Rossiter, 1999). Within evolutionary biology, parental effects are defined as sustained...

Genetics of sexspecific behavior

Considerably less is known about the genetic mechanisms that engender behavioral differences between the sexes in C. elegans. Like the developmental mechanisms discussed above, these differences are controlled by tra-1, though recent evidence suggests that this gene may not completely account for the full extent of sexual dimorphism. Again, DM-domain genes are proving to be critical regulators of this process, as three genes of this family in C. elegans are required for some aspects of...

Monogamy in mammals

The conserved nuclear unit (Wilson, 1975) of the mammalian social group is the maternal-infant interaction, which is a defining mammalian trait. Because mammalian neonates require mother's milk for survival, females (and neonates) face substantial selection pressure to maintain evolved neurobiological mechanisms that support maternal-infant interaction. Even though the mammalian nuclear unit is highly conserved, the quantity of maternal care and the quality of the interaction are not conserved....

Conclusions And Implications For Future Work

MHC genes (as well as yet unknown other genes) contribute to a mouse's individual body odor and these odors are important regulators of behavioral and neuroendocrine functions, including mating choices. In addition to mice, there are evidence that (1) human body odors also may be influenced by HLA genetic variation and (2) these odors may mediate behavioral responses to other people. These findings raise many questions. First, we still do not know how variation in these genes leads to variation...

Acknowledgments

I thank the members of my research group, particularly K. H. Lee, D. A. Mason, R. M. Miller, and W. R. Mowrey, for insightful discussions and critical reading of the chapter. For generously sharing unpublished results and for comments on the chapter, I am grateful to A. Barrios, G. Kleemann, and S. W. Emmons H. Schwartz and H. R. Horvitz J. White and E. M. Jorgensen A. Whittaker and P. W. Sternberg K. L. Chow and T. Liu and M. M. Barr. I also thank WormAtlas (www.wormatlas. org), a valuable...

B Male foodleaving

In laboratory culture, males in the absence of hermaphrodites will leave a food source, often lethally. As this behavior is exhibited only by adult males, and is not expressed when a hermaphrodite is present, it has been interpreted as a male mate-searching or sex-drive behavior (Lipton et al., 2004). While the specific signals that control this behavior have not been identified, one possibility is that the presence of a hermaphrodite inhibits a mate-searching drive state. Interestingly, the...

Sexual dimorphism in the C elegans nervous system

The sex differences exhibited by the C. elegans nervous system are of two general forms. First, and more conspicuous, is the presence of sex-specific neurons in both hermaphrodites and males (Fig. 1.2A Table 1.1). This sex-specific component of the nervous system comprises 8 neurons in hermaphrodites and 89 in males, all of which are thought to function in circuits dedicated to sexually dimorphic behavior. In both sexes, the sex-specific nervous system is overlaid onto the 294 neurons common to...

A Male mating behavior

As a stepwise behavior that must integrate several sensory cues and produce several types of coordinated motor output, male mating is thought to be the most complex behavior encoded in the C. elegans nervous system. As these steps are likely hardwired into the male nervous system, male mating is considered to be an innate behavior. However, it is not unlikely that male mating is regulated by experience, though this remains unexplored. Male mating behavior entails a series of distinct steps...

Caenorhabditis elegans as a model for sex differences in nervous system structure and function

Coordinating the development and function of the multiple attributes that distinguish the sexes of a given species is a significant challenge to the genetic programs that govern metazoan development. Organisms must make a decision, usually early in development, about which sex to become the outcome of this decision then instructs the development of multiple sex-specific structures and guides the sex-specific modification of common structures. This process is particularly complex in the nervous...

BMolecular differences

In addition to these subtle structural differences, two examples of sex differences in gene expression in the core nervous system are known. First, the seven-transmembrane putative chemoreceptor gene srd-1 has been found to be expressed in the ADF sensory neurons only in males, even though these cells are present and appear identical in both sexes (Troemel et al., 1995 White et al., 1986). A second serpentine receptor gene, srj-54, is expressed in the common AIM interneurons in males only (D....

Comparative analysis

It is clear that oxytocin plays a role in maternal-infant interactions, and that it also plays a role in adult social interactions in a manner independent of estrogen priming, at least in monogamous prairie voles. Even though the presence of a mother-infant interaction is a conserved feature of mammals, female bonding with other conspecifics is not universal. Diversity in social behavior among closely related species can be utilized to investigate the neural and genetic mechanisms that...

Placental Regulation Of Maternal Endocrine Function And Behavior

The placenta, developed from the cell lineage of fetal trophectoderm, exerts considerable influence on maternal endocrine function. Progesterone is the steroid hormone that dominates pregnancy and is necessary to sustain pregnancy. High levels of progesterone during pregnancy are a function of the fetal placenta either directly (primates) or indirectly (rodents) by production of placental hormones that sustain the ovarian corpus luteum. Progesterone has a broad spectrum of effects by acting on...

Parentinfant Recognition

Parent-infant recognition based on individual-specific odors is well documented among many genera (Beauchamp et al., 1976 Halpin, 1980 Johnston et al., 1999). We have found (Yamazaki et al., 1992) that H-2 odortypes are evident in mice as young as 1 day of age, raising the possibility that a dam might thereby identify her offspring. Moreover, since olfactory function is well developed in mouse pups as young as a few days of age (Hepper, 1983), they might reciprocally recognize and prefer their...

Relevance for vertebrate systems

How can research in a simple invertebrate illuminate the mechanisms that shape sex differences in the vertebrate nervous system Though C. elegans has a strong history of defining conserved genetic mechanisms critical for neural development and function, the mechanisms used by vertebrates to effect sexual differentiation of the nervous system seem, at first glance, fundamentally different from those in C. elegans. As described above, gonadal hormones have long been considered to be the sole...

Phenotypic variation in human female reproductive development

The most reliable measure of environmental quality in human research is that of socioeconomic status (SES), which predicts multiple health outcomes. Studies, including those using prospective analyses, reveal significant effects of SES during childhood that are statistically independent of those associated with adult SES, on adult mortality (Davey-Smith et al., 1998 Kaplan and Salonen, 1990 Marmot et al., 2001), metabolic (e.g., body mass index, hip waist ratio) and cardiovascular (Barker, 1992...

Environmental adversity and sexual maturation

Studies of the relation between birth weight and puberty reflect the influence of social and economic context on female reproductive function. And as with other developmental outcomes, there is evidence that socioeconomic conditions are mediated by effects on parent-offspring interactions occurring during both the pre- and postnatal periods. Indeed, the ultimate consequences for reproduction depend on environmental adversity prior to and following birth. Belsky et al. (1991) suggested that...

Brain Evolution And Behavior A Role For Genomic Imprinting

In early shrewlike mammals and other small-brained rodents, the brain's regulation of behavior could be viewed as making an integrative contribution to physiological homeostasis. Such small brains may be considered as interfacing between internal bodily needs and the outside world in which the animal survives, serving to provide information about the habitat and social environment. Feeding is stimulated by hunger, sexual behavior is determined by the internal secretion of gonadal hormones, and...

Parental care and reproductive development

These findings suggest a relation between parental care and reproductive development in the offspring. An important question concerns the identity of critical mechanisms for such effects. Phenotypic plasticity in reproductive tactics have been studied from the point of ultimate causation (Tinbergen, 1972), which refers to the impact of such variations on reproductive fitness. In contrast, proximal causation, which refers to more immediate cause-effect relations, such as genomic polymorphisms or...

Sexual differentiation

Sexual differentiation in mammals is linked to the composition of the sex chromosomes. In the genetic male, the sexually determining region (Sry) gene on the Y chromosome promotes the differentiation of the testis from the indifferent gonad, resulting in the production of two critical hormonal signals, testosterone and anti-Mullerian hormone (Arnold, 2004 Breedlove andHampson, 2002 Goy and McEwen, 1980 McCarthy, 1994). These hormones initiate the differentiation of the reproductive tracts and...

Sex Differences In The Rodent Vno Pathway

The rodent vomeronasal system exhibits sexual dimorphisms at multiple levels along its projection pathway. The MeA, BNST, and MPOA are all larger in the male than female, while subsequent projections to the hypothalamic nuclei, particularly those concerned with female endocrine regulation and maternal care, tend to be larger in the female (Segovia and Guillamon, 1996) (Fig. 8.5). Lesions in discrete parts of this projection pathway enhance components of female typical behavior, whereas in the...

B The VC neurons

The VC neurons are cholinergic motor neurons that have synaptic connections to the HSNs and the vm2 vulval muscles (White et al., 1986). The VCs have a more subtle effect on egg-laying behavior, acting to negatively regulate vulval muscle contraction. This function is mediated by their release of acetylcholine, which may inhibit the HSN-mediated stimulation of vulval muscle contraction (Bany et al., 2003). Rather than sex-specific cell death, it is a cell fate change that underlies the sexually...

The Genetics Of Sexual Orientation

Although there is no convincing evidence linking differences in sexual orientation to variations in prenatal androgens, there is abundant evidence for a strong genetic component. Family studies (Bailey and Bell, 1993 Bailey and Benishay, 1993 Bailey and Pillard, 1991 Bailey et al., 1995, 1999 Pattatucci and Hamer, 1995 Pillard, 1990 Pillard and Weinrich, 1986) showed an increased rate of homosexuality in siblings of gays and lesbians and in the maternal uncles of gay men (a median rate of 9 for...

The Central Dogma Of Sexual Differentiation

In the late 1940s, the classic gonad-transfer experiments of Alfred Jost led to the development of the central dogma of sexual differentiation in mammals and birds Jost, 1947, 1970 . According to this view, sexual dimorphisms of somatic tissues are dependent primarily on testicular secretions from the developing fetus. The presence of testes induces male development through the actions of two secreted testicular hormones, Mullerian inhibiting substance and testosterone. Absence of testicular...

Cellular Basis Of fru Functions In Male Courtship Behavior

In neurobiology, it is critical to determine the neural circuit underlying respective behavior. It is a demanding issue to describe neural connections formed by fru-expressing neurons to illustrate the entire network that determines male courtship behavior. To this end, efforts have been made to identify individual neurons that express Fru Billeter and Goodwin, 2004 Manoli et al., 2005 Stockinger et al., 2005 . To identify fru-expressing neurons, it is crucial to obtain reporter strains that...

Introduction

Karlson and Luscher 1959 defined pheromones as substances secreted to the outside of an individual and received by a second individual of the same species in which they release a specific reaction, for example, a definite behavior or developmental process. This new term was created based on identification of a volatile sex attractant, bombykol, that is released by the female silk moth Bombyx mori and elicits the full sexual behavior of male moths Butenandt et al., 1959 . In contrast to such...

BThe CA and CP motor neurons

The only male-specific cells of the ventral nerve cord are the CA and CP motor neurons. Lineally, the CAs and CPs are analogous to the hermaphrodite VC neurons, as they arise from the division of the Pn.aap cells, which either become VC neurons or die in hermaphrodites Fig. 1.3 . In males, the Pn.aap cells do not die this may be the default hermaphrodite fate , but instead remain undifferentiated until they divide during L3 to give rise to one CA and one CP. As discussed above, it is possible...

Daisuke Yamamoto

Division of Neurogenetics, Graduate School of Life Sciences Tohoku University, 6-3 Aoba, Aramaki, Aoba-ku, Sendai Miyagi 980-8578, Japan I. Hypothesis on the Master Control Gene for Behavior II. Discovery of fru Mutants and Their Phenotypic Characteristics III. Molecular Biology of fru Locus IV. Cellular Basis of fru Functions in Male Courtship Behavior V. Conclusions Acknowledgments References fruitless fru , originally identified with its mutant conferring male homosexuality, is a neural sex...

Genomic Imprinting Coadaptive Evolution Of Brain And Placenta

The placental trophoblast is an extraordinary tissue capable of producing a vast range of endocrine secretions, which enable the fetus to regulate its own destiny. Most of these placental hormones function by acting on maternal receptors, an interaction that has required genomic coadaptation between mother and fetus. Hence, the functioning of two genomes maternal and fetal as part of a single phenotype pregnant mother provides a template for coadaptive selection pressures to operate. Early...

Maternal effects on HPG function and mating behavior

In an effort to establish the regional specificity we examined ERa expression in multiple brain regions. To our surprise, we found that ERa mRNA expression is significantly increased in the ventromedial nucleus of the hypothalamus VMNh in the offspring of Low LG mothers. Further studies revealed a significant increase in the AVPV region of the female offspring of Low LG mothers. Estrogen acts through ERs in the AVPV to regulate GnRH with downstream effects on pulsitile LH and ovarian hormone...

Abstract

All rights reserved. 0065-2660 07 35.00 DOI 10.1016 S0065-2660 07 59008-5 Most of the imprinted genes investigated to date are expressed in the placenta and a subset are expressed in both placenta and hypothalamus. Based on phenotypes derived from targeted mutagenesis, a hypothesis is developed for the coadaptive evolution of placenta and hypothalamus, particularly in the context of neurohormonal regulation of maternalism. In small-brained mammals, maternalism...

References

A. 1992 . Sexual orientation and the size of the anterior commissure in the human brain. Proc. Natl. Acad. Sci. USA 89, 7199-7202. Arai, Y., and Matsumoto, A. 1978 . Synapse formation of the hypothalamic arcuate nucleus during post-natal development in the female rat and its modification by neonatal estrogen treatment. Psychoneuroendocrinology 3 1 , 31-45. Arnold, A. P. 1996 . Genetically triggered sexual differentiation of brain and behavior. Horm. Behav. 30 4 ,...

Steroid sensitivity of avian vocal control networks

Comparative studies of the distribution of estrogen and androgen receptors expressing cells in vertebrate brains have shown that the brain regions, which typically contain such cells, are evolutionarily conserved e.g., hypothalamic-preoptic areas or are linked to taxa-specific sexual behaviors Kim et al., 1978 Pfaff, 1980 . Vocal control areas are an example of the latter Bernard et al., 1999 Gahr, 2000 Gahr et al., 1993 Metzdorf et al., 1999 . The classical androgen and estrogen receptors are...

The search for a VNO ligand

Initially, it was thought that pheromonal information is processed by the VNO system and odorants by the main olfactory system. Increasing evidence, however, has suggested that both systems can detect pheromones Baxi et al., 2006 Spehr et al., 2006b Stowers and Marton, 2005 . For example, imaging and electrophysiological techniques have revealed that the volatile urinary pheromones implicated in various intraspecies responses activate both olfactory and vomer-onasal sensory neurons...

The Endocrinology Of Birds Vocalization

Obligate sex-specific vocalizations are either due to brain-intrinsic genetic mechanisms or result from irreversible ontogenetic action of testosterone and its androgenic and estrogenic metabolites. Facultative sex-specific vocalizations might be due to the action of elevated levels of gonadal steroids that could occur repeatedly at various time-windows throughout life. Although there is very good experimental evidence for sex steroids affecting sex-specific vocalizations as in the case of...

Genomic organization of the ESP family

ESP1 turned out to be a member of a large multigene family that was unknown when we reported it in October 2005 Kimoto et al., 2005 . This novel family has been named the ESP family Kimoto et al., 2005 . In October 2005, the ESP family included 24 members, but by May 2006, the number had increased to 38 because there had been many gaps in the region of the ESP gene cluster Fig. 6.4 Kimoto et al., 2006 . Of the 38 ESP genes, 15 are expressed in an exocrine gland around the face area, supporting...

Elizabeth A D Hammock

Department of Pharmacology, Vanderbilt Kennedy Center for Research on Human Development, Vanderbilt University, Nashville, Tennessee 37232 II. Oxytocin and Pair Bonding in Voles III. Vasopressin and Pair Bonding in Voles C. V1aR in the ventral pallidum D. Ventral forebrain reward pathways IV. Gene Regulation in Male Species-Typical Behavior Evolutionary Tuning Knobs Copyright 2007, Elsevier Inc. All rights reserved. 0065-2660 07 35.00 DOI 10.1016 S0065-2660 07 59004-8

The anatomy of avian vocal control networks

In songbirds, neural vocal control is achieved by a chain of interconnected brain areas in the fore-, mid-, and hindbrain Nottebohm et al., 1976 Vates et al., 1997 Vu et al., 1994 Wild, 1997 Yu et al., 1996 . Vocal learning of songbirds correlates with the differentiation of forebrain vocal control areas, the robust nucleus of the arcopallium RA , lateral magnocellular nucleus of the anterior nidopallium lMAN , HVC used as proper name , medial magnocellular nucleus of the anterior nidopallium...

Sven Bocklandt and Eric Vilain

Role of SRY in Sex Determination 246 II. Male and Female Brains are Different 247 III. The Central DOGMA of Sexual Differentiation 247 IV. Sex Hormones in Brain Sexual Differentiation 248 V. Exceptions to the DOGMA 248 VI. Evidence for a Direct Role of SRY in the Brain 250 VII. Sexual Orientation is a Sexually Dimorphic Trait 251 VIII. Homosexual Brains are Different 253 IX. The Role of Prenatal Androgen Exposure on Sexual Orientation Myth or Reality 254 X. Indirect Hormonal Measures 255 XI....