Phenotypic differences in the GnRH neuronal system of deer mice Peromyscus maniculatus under a natural short photoperiod

Korytko, Andrew I.; Vessey, Stephen H.; Blank, James L.

doi:10.1530/jrf.0.1140231

Cited by 7 publications

(8 citation statements)

References 11 publications

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“…P. leucopus selected to retain year-round reproductive competence possess a larger complement of mature GnRHreleasing cells in both SD and LD than mice selected to experience RI. Our results from experiment 1 are consistent with previous findings obtained in an unselected but phenotypically diverse colony of P. maniculatus tested in SD only (23)(24)(25). In addition, our results are consistent with and extend the conclusions from previous experiments on unselected female P. leucopus from a different locality, where variation in photoperiod responsiveness was found to correlate with variation in GnRH cell numbers and location in SD (12).…”

Section: Discussionsupporting

confidence: 92%

“…Previous experiments conducted on an unselected colony of P. leucopus (12) and an unselected colony of P. maniculatus (24,25) suggest differences in GnRH neuronal activity between males of responsive and NR phenotype under an inhibitory photoperiod. The antibodies used in the immunocytochemistry (ICC) of these studies, GnRH-BDB (12) and LR1-GnRH (24,25), are known to preferentially bind to an epitope of pro-GnRH.…”

mentioning

confidence: 91%

“…The antibodies used in the immunocytochemistry (ICC) of these studies, GnRH-BDB (12) and LR1-GnRH (24,25), are known to preferentially bind to an epitope of pro-GnRH. It has been suggested that responsive males, when placed in inhibitory photoperiods, sequester prohormone in the neurons that synthesize GnRH and fail to secrete mature peptide (13,23,25). This implies that phenotypic differences are due to differences in responses of GnRH neurons to photoperiod.…”

mentioning

confidence: 99%

“…In these studies, the majority of the immunoreactive (IR) GnRH neurons of P. maniculatus were found within seven regions in and around the hypothalamus. Significant differences in neuronal location and density between responsive and NR mice could be traced to two of those: the lateral hypothalamus and the preoptic areas (24,25).…”

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confidence: 99%

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Response to selection for photoperiod responsiveness on the density and location of mature GnRH-releasing neurons

Avigdor¹,

Sullivan²,

Heideman³

2005

American Journal of Physiology-Regulatory, Integrative and Comp

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-Natural variation in neuroendocrine traits is poorly understood, despite the importance of variation in brain function and evolution. Most rodents in the temperate zones inhibit reproduction and other nonessential functions in short winter photoperiods, but some have little or no reproductive response. We tested whether genetic variability in reproductive seasonality is related to individual differences in the neuronal function of the gonadotropin-releasing hormone network, as assessed by the number and location of mature gonadotropin-releasing hormonesecreting neurons under inhibitory and excitatory photoperiods. The experiments used lines of Peromyscus leucopus previously developed by selection from a wild population. One line contained individuals reproductively inhibited by short photoperiod, and the other line contained individuals nonresponsive to short photoperiod. Expression of mature gonadotropin-releasing hormone (GnRH) immunoreactivity in the brain was detected using SMI-41 antibody in the single-labeled avidin-biotin-peroxidase-complex method. Nonresponsive mice had 50% more immunoreactive GnRH neurons than reproductively inhibited mice in both short-and long-day photoperiods. The greatest differences were in the anterior hypothalamus and preoptic areas. In contrast, we detected no significant within-lines differences in the number or location of immunoreactive GnRH neurons between photoperiod treatments. Our data indicate that high levels of genetic variation in a single wild population for a specific neuronal trait are related to phenotypic variation in a life history trait, i.e., winter reproduction. Variation in GnRH neuronal activity may underlie some of the natural reproductive and life history variation observed in wild populations of P. leucopus. Similar genetic variation in neuronal traits may be present in humans and other species. genetic variation; artificial selection; seasonality; evolutionary physiology; brain variation; gonadotropin-releasing hormone WITHIN-POPULATION GENETIC VARIATION regulating the abundance, location, and connections of neurons must contribute to evolution of brain function. Similarly, natural genetic variation in neuronal traits is presumably responsible for some proportion of intraspecific functional variation in vertebrates. Because neural circuitry regulates reproductive physiology and behavior, neural variation is likely to explain some unknown proportion of life history variation within as well as among species. At present, almost nothing is known about natural levels of genetically based neuroendocrine physiological variation related to life history variation within species of mammals. The physiological link between genes and life history patterns is important because genes must act on life history traits through physiological mechanisms, and thus physiological variation may shape or constrain life history evolution (16). Understanding natural neuroendocrine variation related to life history traits might help us learn how rapidly brains adapt to current cha...

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Section: Discussionsupporting

confidence: 92%

mentioning

confidence: 91%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Response to selection for photoperiod responsiveness on the density and location of mature GnRH-releasing neurons

Avigdor¹,

Sullivan²,

Heideman³

2005

American Journal of Physiology-Regulatory, Integrative and Comp

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“…Other factors, including food and age, can affect reproductive responses to season (Blank, 1992;Heideman, 2004;Prendergast et al, 2001), indicating that some variation in seasonal reproduction is environmental. Heideman et al (Heideman, 2004) and others (Blank, 1992;Korytko et al, 1998) have used natural variation in these populations to study causes of intraspecific differences in seasonal reproduction. Lines of white-footed mice created by artificial selection from a single wild population (Heideman et al, 1999a) are being used to study natural genetic variation in this pathway.…”

Section: Regulation Of the Seasonal Timing Of Reproductive Behaviormentioning

confidence: 99%

Behavioral neuroendocrinology in nontraditional species of mammals: Things the ‘knockout’ mouse CAN'T tell us

Smale

Heideman

French

2005

Hormones and Behavior

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The exploration of many of the fundamental features of mammalian behavioral neuroendocrinology has benefited greatly throughout the short history of the discipline from the study of highly inbred, genetically characterized rodents and several other "traditional" exemplars. More recently, the impact of genomic variation in the determination of complex neuroendocrine and behavioral systems has advanced through the use of single and multiple gene knockouts or knockins. In our essay, we argue that the study of nontraditional mammals is an essential approach that complements these methodologies by taking advantage of allelic variation produced by natural selection. Current and future research will continue to exploit these systems to great advantage and will bring new techniques developed in more traditional laboratory animals to bear on problems that can only be addressed with nontraditional species. We highlight our points by discussing advances in our understanding of neuroendocrine and behavioral systems in phenomena of widely differing time scales. These examples include neuroendocrine variation in the regulation of reproduction across seasons in Peromyscus, variation in parental care by biparental male rodents and primates within a single infant rearing attempt, and circadian variation in the regulation of the substrates underlying mating in diurnal vs. nocturnal rodents. Our essay reveals both important divergences in neuroendocrine systems in our nontraditional model species, and important commonalities in these systems.

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Genetic variation in total number and locations of GnRH neurons identified using in situ hybridization in a wild-source population

et al. 2015

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The evolution of brain function in the regulation of physiology may depend in part upon the numbers and locations of neurons. Wild populations of rodents contain natural genetic variation in the inhibition of reproduction by winter-like short photoperiod, and it has been hypothesized that this functional variation might be due in part to heritable variation in the numbers or location of gonadotropin releasing hormone (GnRH) neurons. A naturally variable wild-source population of white-footed mice was used to develop lines artificially selected for or against mature gonads in short, winter-like photoperiods. We compared a selection line that is reproductively inhibited in short photoperiod (Responsive) to a line that is weakly inhibited by short photoperiod (Nonresponsive) for differences in counts of neurons identified using in situ hybridization for GnRH mRNA. There was no effect of photoperiod, but there were 60% more GnRH neurons in total in the Nonresponsive selection line than the Responsive selection line. The lines differed specifically in numbers of GnRH neurons in more anterior regions, whereas numbers of GnRH neurons in posterior areas were not statistically different between lines. We compare these results to those of an earlier study that used immunohistochemical labeling for GnRH neurons. The results are consistent with the hypothesis that the selection lines and natural source population contain significant genetic variation in the number and location of GnRH neurons. The variation in GnRH neurons may contribute to functional variation in fertility that occurs in short photoperiods in the laboratory and in the wild source population in winter.

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Phenotypic differences in the GnRH neuronal system of deer mice Peromyscus maniculatus under a natural short photoperiod

Cited by 7 publications

References 11 publications

Response to selection for photoperiod responsiveness on the density and location of mature GnRH-releasing neurons

Response to selection for photoperiod responsiveness on the density and location of mature GnRH-releasing neurons

Behavioral neuroendocrinology in nontraditional species of mammals: Things the ‘knockout’ mouse CAN'T tell us

Genetic variation in total number and locations of GnRH neurons identified using in situ hybridization in a wild-source population

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