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Poster Full Abstracts - Gametogenesis and Organogenesis
Poster board number is above title. The first author is the presenter
287
unknown. In order to further understand the working components of this system, specific deletions within the second chromosome were studied. The study
was conducted systematically by beginning with larger deletions that had previously shown distortion and slowly reducing the size of the deletion. When
these deletion stocks were combined with
SD-5
r7
, with
Rsp
s
on the Y it was found that a deletion of the region 26C1;26D1 displayed distortion whereas a
deletion of the region 26C3;26D1 did not. When a deletion of the 26C2;26C3 region was crossed with
SD-5
r7
distortion was observed. Within this region the
genes
Cpr
and
Gef26
are of particular interest. Stocks containing a mutation in
Cpr
did not demonstrate distortion when combined with
SD-5
r7
. However,
when a stock containing a mutation in the gene
Gef26
was combined with
SD-5
r7
, distortion was noted. These results suggest that better understanding of the
gene
Gef26
, and its function within the cell during spermatogenesis, would shed some light as to how segregation distortion takes place on a molecular level.
583A
Phosphoinositides regulate nuclear morphogenesis in Drosophila.
Lacramioara Fabian
1
, Julie Brill
1,2
. 1) Cell Biology, The Hospital for Sick Children,
Toronto, Ontario, Canada; 2) Molecular Genetics, University of Toronto, Ontario, Canada.
Spermatid nuclei undergo dramatic changes in shape and chromatin condensation during the late stages of sperm development. Histones that package the
DNA in early spermatids are replaced by the smaller protamines, which further remodel and package the chromatin into the long, thin mature sperm nucleus.
These changes are also associated with microtubule-dependent nuclear elongation, when the perinuclear microtubule cytoskeleton is reorganized to provide
additional support to the elongating nucleus. Here, we show that levels of phosphatidylinositol phosphates (PIPs) are critical for shaping the sperm head and
for chromatin condensation during Drosophila spermiogenesis. Spermatids in which levels of phosphatidylinositol 4,5-bisphosphate (PIP2) have been
reduced show profound defects in nuclear shaping; the nuclei do not mature and the males are sterile. Posttranslational modification of histones is impaired
and their removal is delayed. Protamines get incorporated into nuclei despite histones not being completely removed. Transition proteins are missing in these
spermatids. Localization of inner nuclear membrane proteins is defective and repair of double-stranded DNA breaks is incomplete. Our present data suggest
that normal levels of PIP2 are required to coordinate interactions between the nuclear membrane, chromatin and the cytoskeleton.
584B
A testis-enriched predicted ATP synthase subunit required for mitochondrial shaping during spermatogenesis.
Yihharn Hwang, Lauren Ivey, Karen
G. Hales. Department of Biology, Davidson College, Davidson, NC.
ms(2)1400
is a recessive mutation that causes sterility in male
Drosophila melanogaster
by affecting mitochondrial shaping in sperm cells. During
spermatogenesis from the transition between the onion stage to the leaf blade stage, the Nebenkern in spermatids from homozygous
ms(2)1400
males is
unable to properly unfurl into two distinct mitochondrial derivatives due to defects in the internal structure of the membranes of the Nebenkern. The
mitochondria remain unelongated as the flagellar axoneme grows, leading to non-motility of mature sperm. Through deficiency mapping experiments and
candidate gene analysis, the
ms(2)1400
mutation was suspected to be in gene
CG7813
.
CG7813
encodes a predicted paralog of ATP synthase subunit d that
shows enriched expression in the
Drosophila
testis. ATP synthase dimerization in the mitochondrial inner membrane is known to affect cristae morphology
in other organisms. We confirmed that
CG7813
represents
ms(2)1400
using RNAi via the GAL4-UAS system to trigger gene knockdown in the testis. Testis
preparations from
CG7813
RNAi flies were compared to those from homozygous flies with the
ms(2)1400
mutation. We observed distinct phenotypic
similarity and thus confirmed location of
ms(2)1400
in
CG7813
. A second technique, EMS mutagenesis, is currently in progress to generate a
ms(2)1400/CG7813
allelic series and thus to broaden our functional understanding of this gene product. Confirmation of
ms(2)1400
as
CG7813
provides
new information of the role of ATP synthase variants in tissue-specific mitochondrial morphology. We suspect that the unusually large ATP synthase
subunit d encoded by wild type
ms(2)1400/CG7813
may normally alter dimerization of the complex to enable the specialized Nebenkern internal structure.
The functions of three other testis-enriched paralogs of ATP synthase subunits, b, g and F6, are being similarly explored.
585C
Loss of
Odysseus
function affects male fertility by decreasing germ cell numbers in
Drosophila melanogaster
.
Chau-Ti Ting
1
, Ya-Jen Cheng
2
, Shun-
Chern Tsaur
3
, Shu Fang
4
. 1) Department of Life Science; Institute of Ecology and Evolutionary Biology; Institute of Zoology; Research Center for
Developmental Biology and Regenerative Medicine, National Taiwan University, Taiwan, ROC; 2) Institute of Molecular and Cellular Biology, National
Tsing Hua University, Taiwan, ROC; 3) Department of Life Sciences & Institute of Genome Sciences, National Yang-Ming University, Taiwan, ROC; 4)
Biodiversity Research Center, Academia Sinica, Taiwan, ROC.
Loss of a testis-specific expression of
Odysseus
(
OdsH
) has been shown to cause male fertility defect in
Drosophila melanogaster
, but the underlying
mechanisms at the cellular level is unknown. To address the possible mechanisms and functional roles of
OdsH
in
spermatogenesis
, we compared the cell
numbers at different developmental stages during spermatogenesis between the
OdsH
null mutant and wild-type flies. Our results showed that the number of
early developing germ cells, including spermatogonia and spermatocytes, is reduced in the
OdsH
mutant males. In addition, the number of germline stem
cells in aged males is also reduced, presumably as a result of the disruption of germline stem cell maintenance, which leads to more severe fertility defect.
These findings suggest that the function of the enhancement of sperm production by
OdsH
is to act across all the ages of males.
586A
Determining the molecular roles of
CG4701
and
nmd
in
Drosophila melanogaster
spermatogenesis through analysis of β-tubulin and anillin
localization.
Bethany L Wagner, Sarah C Pyfrom, Karen G Hales. Department of Biology, Davidson College, Davidson, NC.
Mutations in
CG4701
cause recessive male sterility with defects at particular stages of spermatogenesis such as meiosis, meiotic cytokinesis, and early
post-meiotic spermatids.
nmd
is a broadly-expressed and essential paralog of
CG4701
; two different hypomorphic
nmd
alleles also affect spermatogenesis.
In
CG4701
mutants, we observed vacuolated Nebenkerne, some of which were abnormally large, suggesting meiotic cytokinesis defects. In one of the
hypomorphic male-sterile nmd alleles, mitochondria do not aggregate properly so the Nebenkern never forms; in the other strain, there is a malfunction
during cytokinesis, so it is phenotypically very similar to
CG4701
. CG4701 and Nmd belong to the AAA ATPase family of proteins and are related to
spastin and katanin, known microtubule-severing proteins. Nmd localizes to mitochondria and centrosomes/basal bodies, and attempts are underway to
localize CG4701. β-tubulin and anillin (a contractile ring component) are proteins essential to spermatogenesis, particularly in the stages most affected by
CG4701
and
nmd
. Since we hypothesized β-tubulin and anillin function to be impaired in the mutants, we compared their localization in normal