Mh. Lin et al., ECTOPIC EXPRESSION OF MEF2 IN THE EPIDERMIS INDUCES EPIDERMAL EXPRESSION OF MUSCLE GENES AND ABNORMAL MUSCLE DEVELOPMENT IN DROSOPHILA, Developmental biology, 182(2), 1997, pp. 240-255
Myocyte-specific enhancer-binding factor 2 (MEF2) is a myogenic regula
tory factor in vertebrates and Drosophila. Whereas the role of MEF2 in
regulating vertebrate myogenesis and muscle genes has been extensivel
y studied, little is known of the role of MEF2 in regulating Drosophil
a myogenesis. We have shown in a recent analysis of the regulation of
the Drosophila Tropomyosin I (TmI) gene in transgenic flies that MEF2
is a positive regulator of TmI expression in the somatic body-wall mus
cles of embryos, larvae, and adults. To understand further the role of
MEF2 in myogenesis and test the role of MEF2 in regulating TmI expres
sion, we have used the yeast GAL4/UAS system to generate embryos in wh
ich MEF2 is ectopically expressed in tissues where it is not normally
expressed or embryos in which MEF2 is overexpressed in the mesoderm an
d muscles. We observe that ectopic expression of MEF2 in the epidermis
and the ventral midline cells in embryos activates the expression of
TmI and other muscle genes in these tissues and that this activation i
s stage-dependent suggesting a requirement for additional factors. Fur
thermore, ectopic expression of MEF2 in the epidermis results in a dec
rease in the expression of signaling molecules in the epidermis and a
failure of the embryo to properly form body-wall muscles. These result
s indicate that MEF2 can function out of context in the epidermis to i
nduce the expression of muscle genes and interfere with a requirement
for the epidermis in muscle development. me also find that the level o
f MEF2 in the mesoderm and/or muscles in embryos is critical to body-w
all muscle formation; however, no effect is observed on the developmen
t of the visceral muscle or dorsal vessel. (C) 1997 Academic Press.