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Poster Full Abstracts - Pattern Formation
Poster board number is above title. The first author is the presenter
321
Ontario, Canada.
The Homeotic selector (Hox) genes are required for body patterning in Bilaterans. In Drosophila melanogaster, Hox expression along the anterior-posterior
axis of the embryo establishes segmental identity. The Hox gene, Sex combs reduced (Scr), is essential for the identity of the labial and prothoracic
segments. A characterization of 15 Scr mutant alleles identified Scr14, a missense allele in the evolutionarily-conserved octapeptide motif. Scr14 was
initially grouped as an antimorphic allele, but distinct properties were noted resulting in its reclassification. In the classic mechanism for an antimorphic
allele, dominant negativity, inactive proteins expressed from the mutant allele form a complex with wildtype proteins rendering the complex inactive. Scr14
is distinct from the traditional dominant negative because SCR14 alone has wildtype activity; inactivation is only observed in the presence of other SCR
polypeptides. We observed a significant reduction in sex comb bristle number on the prothoracic legs of Scr+/Scr14 males, indicating formation of inactive
complexes between SCR+ and SCR14 proteins. A further decrease in Scr activity occurred when truncated SCR null peptides (with wildtype octapeptides)
were expressed with SCR14, due to only SCR14 homodimers being active. Surprisingly, truncated SCR14 peptides expressed in vivo did not inhibit
endogenous SCR+. In contrast, expression of truncated SCR+ peptides suppressed endogenous SCR14 activity, showing that the effect of the Scr14
missense mutation is non-reciprocal. This may explain why in vitro experiments failed to show complex formation with SCR+. Currently, we are trying to
demonstrate stable complex formation between SCR14 and truncated SCR+ peptides. The observation of non-reciprocality suggests that in Scr+/Scr14 flies
it is the wildtype allele that acts antagonistically to the mutant allele, not the reverse. Scr14 represents a novel class of alleles we have termed: anti-dominant
negative.
709A
The role of disco in specification of the Drosophila leg.
Juan Bautista Rosario. Genetics Dept, North Carolina State Univ, Raleigh, NC.
In Drosophila, the origin of the appendages is established during embryogenesis as a group of cells are set aside to from the imaginal discs. The imaginal
discs have been studied as a paradigm for understanding the genetic control of organ development, and a model describing this process to understand how
the leg develops has been proposed but some questions remain unanswered. The finding that ectopic expression of the Drosophila disco gene in the dpp
domain (Patel et al. 2007) suggest that this model is incomplete, as well as raises questions about imitation of leg primordial and transdetermination. I will
present further data on the transformation caused by ectopic disco, addressing the molecular basis of the transformation and how this relates to normal leg
development. Further, I will present new information about the normal role of the Disco protein during leg development as well as a new role in the
regulation of a Distal-less enhancer previously identified as an early cis-regulatory element expressed in the thoracic imaginal disc primordial during
embryogenesis.
710B
New allele of
engrailed
associated with three spermathecae in
Drosophila melanogaster
female.
Masanobu Itoh
1,2
, Akiko Sawada
3
. 1) Center for
Bioresource Field Science, Kyoto Inst Tech, Kyoto, Japan; 2) Insect Biomedical Research Center, Kyoto Inst Tech, Kyoto, Japan; 3) Dept. Applied Biology,
Kyoto Inst Tech, Kyoto, Japan.
We isolated a recessive mutation (
NK14
) in number of the spermathecae in
Drosophila melanogaster
from the wild population. Females of
NK14
have
three, but not two, functional spermathecae with the penetrance of 95% or more. We investigated the gene(s) responsible for this female specific
morphological abnormality. Chromosome mapping using the balancer chromosomes demonstrated that the responsible gene(s) for the
NK14
phenotype are
mainly located to the second chromosome and some additional genes on the third chromosomes show an epistatic enhancement the
NK14
phenotype.
Moreover,
NK14
showed a partial complementation with
en
spt
, of which females are also known to have a variety in number of the spermathecae depending
on the developmental temperature, although
NK14
females show no temperature-sensitivity. By determining the structure of
engrailed
gene, a deficiency of
15 nucleotides was found in the first exon of
en
gene in
NK14
. The deficiency results in an amino acid substitution (S/T) and a deletion of five consecutive
amino acid residues in EN, which may causes a structural impediment of normal EN function. Our results suggest that
NK14
is a novel allele of
engrailed
gene.
711C
Identification of the gene responsible for the
wings apart
phenotype in
Drosophila melanogaster
.
Ginny Morriss, Carmelita Jaramillo, Bianca Garcia,
Richard Cripps. Biol, Univ New Mexico, Albuquerque, NM.
The Drosophila
wings apart
(
wap
) locus contains a semi-lethal gene that when mutated leads to the absence of the Tergal Depressor of Trochanter (TDT or
jump) muscle.
wap
has been mapped to the proximal X chromosome but it is unclear what gene is mutated to produce the
wap
phenotype. The aspect of
muscle development disrupted in
wap
mutants leading to TDT loss is also unknown. To identify the
wap
gene, we performed complementation mapping of
wap
mutants crossed with known X chromosome deletions. We sectioned thoraces of progeny from these crosses to observe if these flies exhibit the TDT
phenotype associated with
wap
. Results of mapping analysis and phenotypic characterization suggest the most likely candidate for the
wap
gene is
DIP1
.
PCR of
DIP1
is underway in wild-type and wap mutant flies to detect the mutation leading to the observed phenotype. We detected an alanine to threonine
amino acid substitution in the
DIP1
coding region in
wap
9
mutants. Excision of
DIP1
was carried out to determine if the
wap
mutant phenotype could be
reproduced. Excisants exhibit the same semi-lethal phenotype observed in
wap
mutants. These flies are being sectioned to determine if they also exhibit the
TDT phenotype characteristic of
wap
mutants. The results of these excision experiments will be presented. Gain-of-function assays are in progress to
determine if over-expression of
DIP1
rescues the
wap
mutant phenotype. The impact of the
wap
mutation will be analyzed by determining at which step in
development jump muscle formation is disrupted. Results indicate that TDT founder cells are specified early but are lost later in development. The broad
goal of this research is to identify mechanisms of muscle formation in the
Drosophila
adult. Since similar developmental mechanisms are used in vertebrate
and invertebrate muscle formation, this study can aid in understanding processes which may impact vertebrate muscle formation and whose mis-regulation
may lead to muscular diseases.
712A
An interdisciplinary approach to studying the evolution of BMP signaling.
Matthew G. Niepielko
1,2
, Kuhn Ip
2,3
, Jitendra S. Kanodia
4
, Desmond S.
Lun
2,3
, Nir Yakoby
1,2
. 1) Biology Department, Rutgers University, Camden, NJ 08102, USA; 2) Center for Computational and Integrative Biology, Rutgers