Comparative genetics of the central nervous system in epigean and hypogean Astyanax mexicanus
The extreme environment of subterranean caves presents an adaptive challenge to troglobitic organisms. The mechanisms by which natural selection modify an ancestral surface neural circuit to produce a novel subterranean behavior remain a mystery. To address this question, we performed cross species microarray experiments to compare differences in gene expression levels in the adult brain of the teleost Astyanax mexicanus. This species provides a unique opportunity for comparative genetic studies as it consists of extant epigean (surface) and hypogean (cave) conspecifics. Microarray experiments herein revealed significant changes in transcription levels of seventeen genes, several of which are important for behaviors involved in metabolic management. We focused on genes central to three neurotransmission and neuromodulation networks: the endocannabinoid system (Cannabinoid receptor CB1), the dopaminergic system (Tyrosine 3-monooxygenase/tryptophan 5-monooxygenase activation protein) and the glutamatergic system (glutamate receptor AMPA 2a). All three genes were upregulated in the hypogean form of A. mexicanus compared to the epigean form, indicating that behavioral differences in the hypogean form of the species could be due to alterations in expression levels of several key genes. This information provides insights into the complex relationships among environmental factors, genetics, nervous systems and adaptive behavior, and can subsequently help us understand how these interactions affect behavior in other biological systems.
KeywordsBrain Microarray Evolution Astyanax mexicanus CB1 AMPA 2a Tyrosine 3-monooxygenase
Central nervous system
We would like to thank Dr. Gal Haspel and Tzur Haspel-Soares with the production of Fig. 1 and helpful comments; and Dr. Emma Coddington and Dr. Meghan Porter for their input.
- Barr TC (1968) Cave ecology and the evolution of troglobites. Evol Biol 2:35–102Google Scholar
- Culver DC, Pipan T (2009) Biology of Caves and Other Subterranean Habitats. Oxford University Press, Oxford, UKGoogle Scholar
- Li C, Wong WH (2001b) Model-based analysis of oligonucleotide arrays: model validation, design issues and standard error application. Genome Biol 2(8):research0032.1–0032.11Google Scholar
- Mitchell RW, Russell WH, Elliot WR (1977) Mexican eyeless characin fishes, genus astyanax: environment, distribution, and evolution. Spec Publ Mus Texas Tech Univ 12:1–89Google Scholar
- Osei-Hyiaman D, DePetrillo M, Pacher P, Liu J, Radaeva S, Bátkai S, Harvey-White J, Mackie K, Offertáler L, Wang L, Kunos G (2005) Endocannabinoid activation at hepatic cb1 receptors stimulates fatty acid synthesis and contributes to diet-induced obesity. J Clin Investig 115(5):1298–1305PubMedGoogle Scholar
- Oswald RE (2004) Advances in protein chemistry. In: Advances in Protein Chemistry, vol 68 Elsevier, pp 313–349Google Scholar
- Poulson T (1964) Handbook of physiology, section iv, adaptation to the environment. In: Handbook of Physiology, Section IV, Adaptation to the Environment. Am Physiol Soc. pp 749–771Google Scholar
- Ravinet Trillou C, Arnone M, Delgorge C, Gonalons N, Keane P, Maffrand JP, Soubrie P (2003) Anti-obesity effect of sr141716, a cb1 receptor antagonist, in diet-induced obese mice. Am J of Physiol Regul Integr Comp Physiol 284(2):345Google Scholar
- Valenti M, Cottone E, Martinez R, De Pedro N, Rubio M, Viveros MP, Franzoni MF, Delgado M, Di Marzo V (2005) The endocannabinoid system in the brain of Carassius auratus and its possible role in the control of food intake. J Neurochem 95:662–672. doi: 10.1111/j.1471-4159.2005.03406.x PubMedCrossRefGoogle Scholar
- Wilkens H (1988) Evolution and genetics of epigean and cave astyanax fasciatus (characidae, pisces), support for the neutral mutation theory. Evol Biol 23:271–367Google Scholar