The Development of Circadian Rhythms in Human Infants

11.7 Measurement of peripheral gene expression and changes with age
Can the genetic output of the clock be measured in human infants from buccal
swabs and are there any longitudinal changes with age?
The longitudinal description of the ontogeny of circadian rhythmicity for clock gene
expression has not been attempted in human infants. The initial genes of interest
Clock, Bmal1 and Period were substituted with a proxy gene H3f3b, expressed in
peripheral buccal tissue and is thought to reflect the activity of the central clock
(Maxson et al., 1983). H3f3b codes for a histone protein and can be isolated from
buccal swabs. It was not known, prior to the commencement of this project, if cells
from infant swabs were suitable for genetic analysis investigating developmental gene
expression. Could sufficient genetic material be isolated from infant cells to allow
meaningful analysis? What techniques would allow maximum RNA extraction? Was
there any evidence of cycling of the peripheral gene in human tissue from infant
buccal swabs? Would there be any evidence of a link to developmental process and
did the gene expression relate in any way to physiological maturation?
H3f3b was successfully extracted from infant buccal cells and shown to cycle in
peripheral tissue.
A distinct pattern of peripheral cycling gene expression was identified for each infant,
with a change occurring with increase in age. There was in the main, an increase in
amplitude and the goodness of fit to a sinusoidal curve. It is the examination of
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