Genetic control of differential baseline breathing pattern.
Tankersley, Clarke G., Robert S. Fitzgerald, Roy C. Levitt, Wayne A.
Mitzner, Susan L. Ewart, and Steven R. Kleeberger.
Departments of Environmental Health Sciences and Anesthesiology,
The Johns Hopkins University, Baltimore, Maryland 21205
APStracts 3:0498A, 1996.
The purpose of the present study was to determine the genetic control
of baseline breathing pattern by examining the mode of inheritance
between two inbred murine strains with differential breathing
characteristics. Specifically, the rapid, shallow phenotype of the
C57BL/6J (B6) strain is consistently distinct from the slow, deep
phenotype of the C3H/HeJ (C3) strain. The response distributions of
segregant and non-segregant progeny were compared to the two
progenitor strains to determine the mode of inheritance for each
ventilatory characteristic. The BXH recombinant inbred strains (BXH
RI) derived from the B6 and C3 progenitors were examined to establish
strain distribution patterns for each ventilatory trait. To establish
the mode of inheritance, baseline breathing frequency (f), tidal
volume, and inspiratory time (TI) were measured five times in each of
178 mature, male animals from the two progenitor strains and their
progeny using whole-body plethysmography. With respect to f and TI,
the two progenitor strains were consistently distinct, and
segregation analyses of the inheritance pattern suggest that the most
parsimonious genetic model for response distributions of f and TI is
a two locus model. In similar experiments conducted on 82 mature,
male animals from 12 BXH RI strains, each parental phenotype was
represented by one or more of the RI strains. Intermediate phenotypes
emerged to confirm the likelihood that parental strain differences in
f and TI were determined by more than one locus. Taken together,
these studies suggest that the phenotypic difference in baseline
respiratory timing between male B6 and C3 mice is best explained by a
genetic model which considers at least two loci as major
determinants.
Received 26 February 1996; accepted in final form 22 October
1996.
APS Manuscript Number A184-6.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 13 November 1996