I-P-049Strain differences in Tph2 genotype in murine myenteric neurons
Section snippets
Purpose
The Tph2 gene encodes tryptophan hydroxylase 2, the serotonin (5-HT) synthesizing enzyme expressed by central neurons [1]. Brainstem tissue from certain inbred mouse strains is homozygous for a single-nucleotide polymorphism (C/G) in Tph2 at position 1473 that is functionally significant [2]. This study determined the Tph2 genotype of myenteric serotonergic neurons in jejunum of two mouse strains to assess their suitability as natural models of neural 5-HT activity in the enteric nervous system.
Methods
C57Bl/6 (n = 4; The University of Melbourne, VIC, Australia) and Balb/c (n = 3; Animal Resource Centre, WA, Australia) mice were killed by CO2 asphyxiation; the brainstem and jejunum were removed. Myenteric plexus with attached longitudinal muscle was cleared of all mucosa and washed in sterile phosphate buffered saline. Genotyping was performed using the modified tetra-primer amplification refractory mutation system-polymerase chain reaction (PCR) method and primers designed by Zhang et al. [2].
Results
In both brainstem (medulla) and myenteric plexus, 3 of 3 Balb/c mice were homozygous for the 1473G allele. Similarly, 4 of 4 C57Bl/6 mice were homozygous for the 1473C allele in both brainstem and myenteric plexus.
Conclusion
These data confirm the inference that tph2 is expressed by myenteric neurons as well as central neurons. In addition, the confirmation that known strain differences in brainstem tph2 genotype extend to gut has functional implications. This study establishes that Balb/c mice are potential natural models for low 5-HT activity in the enteric nervous system, while C57Bl/6 mice are potential natural models for higher enteric neural 5-HT activity. This finding may allow in vitro and in vivo
References:
[1] Walther, D.J., Peter, J.-U., Bashammakh, S. et al., Science, 299 (2003) 76.
[2] Zhang, X.D., Beaulieu, J.M., Sotnikova, T.D. et al., Science, 305 (2004) 217–217.