Biology Reference
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emergent view is that bile acid-like steroidal biosynthetic pathways in nem-
atodes strikingly resemble those found in mammals. Interestingly long-lived
dwarf mice have alternations in bile acid levels (
Amador-Noguez et al.,
2007
). Knowledge of these biosynthetic pathways may provide novel ave-
nues for manipulating signaling pathways and enhancing animal longevity.
2.4. DA production is distributed
DAF-12 is found in the nucleus of cells throughout the body, but the hor-
mone biosynthetic genes are expressed in discrete steroidogenic tissues
(
Fig. 7.3
). The most important enzyme in the pathway DAF-9/CYP27A1
is found in a pair of neuroendocrine cells called the XXX, the hypodermal
syncytium, and the hermaphrodite spermatheca (
Gerisch et al., 2001; Jia
et al., 2002
). By contrast, DAF-36/Rieske oxygenase is found primarily
in the gut and does not overlap with DAF-9, while DHS-16 resides in sen-
sory neurons, pharynx, and hypodermis (
Rottiers et al., 2006; Wollam et al.,
DAF-36
HMC
INT
NEU
SE
DHS-16
NEU
HYP
PHA
DAF-9
HYP
XXX
SPE
HSD-1
XXX
Figure 7.3 Expression patterns of the DA hormone biosynthetic genes. Expression pat-
terns are based on GFP fusion proteins. Intestine (int), unidentified head neurons (neu),
head mesodermal cell (hmc), seam cells (se), pharynx (pha), hypodermis (hyp) XXX neu-
roendocrine cells (XXX), spermatheca (spe).
