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Drosophila eye model to
study axial patterning, cell survival & birth defects.
The fruit fly, Drosophila melanogaster,
eye serves as an excellent model to study cell type
specification during development. Drosophila eye
has been extensively used to address diverse biological
processes like patterning cell proliferation, cell
death, cell survival, polarity and genetic basis of
human diseases. The compound eye of an adult fly
develops from the primordium called eye imaginal disc
harbored inside larva, which initiates from a group of
20- cells as early as an embryo (Fig. 1).
  
Fig.1 The compound eye
of Drosophila comprising of 800 unit eyes,
ommatidia, initiates from eye-antennal (E.A.) primordium
present in the embryo (A), which grows into larval E.A
imaginal disc (B). E.A imaginal disc give rise to adult
eye (C), which comprises of dorsal (red) and ventral
(blue) compartments antenna (green) and adult head
structures. (Dorsal up and ventral down).
Axial Patterning: Dorso-ventral
patterning in Drosophila eye.
Axial patterning is hallmark of
organogenesis which results in transition of a single
sheet of cells into a 3-D organ. Our lab is interested
in understanding the molecular genetic basis of the
Dorso-ventral patterning, the first lineage restriction
event of early eye primordium. DV patterning thus plays
a crucial role in inducing growth and patterning of
early eye disc. The dorsal and ventral domains of the
eye are generated by the domain specific expression and
function of the dorsal selector genes and the ventral
growth controlling genes. Our results show that
antagonistic interactions between dorsal and ventral
genes define the dorso-ventral eye boundary or equator.
Our lab will focus on identifying new components of DV
patterning and their role in retinal determination of
the eye.
Fig. 2. Ventral is the
ground state of the early eye.
Early
larval eye primordium arises from an initial ventral
state which require ventral gene function. Later, when
dorsal genes expression
emerges in the eye disc Dorsal-Ventral
(DV) axis specification of the eye takes place. DV axis
is the first axis defined in Drosophila eye
(Singh & Choi,
2003)
Cell Survival:
Early development of an organ
primordium is marked by the rapid growth phase until a
threshold of cell number is attained which allow
differentiation process to begin. Our interest is to
identify the genes which are required for cell survival
during this early rapid growth phase. We have found that
DV patterning genes also play this crucial role of cell
survival during early eye development. Our focus would
be to understand the mechanism and to identify the
downstream components of this pathway.
Birth defects:
"Birth defects
are the single leading cause of infant mortality. While
we've made great strides in recent years, the causes of
over 70 percent of birth defects remain unknown. The
collective habilitation costs for these children surpass
$1 billion dollars annually, a cost that pales to
insignificance when compared to the physical and
psychological impact of these birth defects on the
affected children and their families. Despite
unprecedented strides in molecular genetics, brought
about through sequencing of the human genome, the causes
of greater than 60% of all birth defects remain unknown.
Our laboratory seek to provide a better understanding of
the molecular, genetic, and environmental basis of
normal eye development, as well as elucidate the genes
and molecules that when altered result in the genesis of
birth defects in eye.
Fig.3. Mutations in DV
eye patterning- and RD- genes like eyeless/ PAX-6 in
Drosophila results in (B) No-eye, (A) Wild-type eye.
(C, D) A range of birth defects like loss of eye
field are seen in the newborns. Genetic basis of these
birth defects in eye is far from complete. |
