Tag: Developmental Biology

The Role Of Patterned Spontaneous Circuit Activity In Drosophila Neuronal Circuit Assembly

Presenter(s):Nelson Perez − Biology

Faculty Mentor(s): Arnaldo Carreira-Rosario, Chis Doe

Oral Session 2SW

Research Area: Natural sciences, Neuroscience, Biology, Developmental Biology

Funding: HHMI (Howard Hughes Medical Institute), SPUR Program

Neuronal networks become active before they are fully functional. This is known as patterned spontaneous network activity (PaSNA), an event characterized by quiescent periods followed by bursts of activity. Many studies have demonstrated the importance of PaSNA for proper neuronal circuit assembly. Yet, little is known about the mechanisms underlying PaSNA.
In the Drosophila ventral nerve cord (spinal cord for invertebrate counterpart) PaSNA occurs during late embryonic stages. During PaSNA, embryos exhibit intermittent episodes of uncoordinated motor activity that gradually mature into crawling waves. Concomitantly with wave maturation, more neurons become active during PaSNA. The identity of these neurons and function during PaSNA remains unknown. To identify which cells undergo PaSNA and their function during circuit assembly, we are screening for GAL4 lines, which maintain expression in small subsets of neurons from the onset of PaSNA until the circuit is fully assembled. We have identified several GAL4 lines suitable for our experiments. Using in vivo calcium imaging, we identified that the neurons labeled by one of these lines participates in PaSNA. Four other lines have been identified as good candidates for future experiments that involve calcium imaging and tracking of synapsis formation during PaSNA. This represents a unique tool to study PaSNA and its role in circuit formation.

Effect of Elevated Temperature on Embryonic Skeletal Development in Antarctic Bullhead Notothen, Notothenia coriiceps

Presenter(s): Natalie Mosqueda − Biology

Faculty Mentor(s): John Postlethwait, Thomas Desvignes

Poster 70

Research Area: Developmental Biology

Funding: SPUR NIH Grant

Among adapted species is the Antarctic Bullhead Notothen, Notothenia coriiceps, a Notothenoid only found in the secluded waters of the Southern Ocean. The Antarctic Peninsula in particular is one of the faster warming areas, warming at a rate 10 times faster than the global average and is expected to rise 4°C from the normal -1/0°C at the end of the century. It is important to investigate the effects of the warming temperature on embryogenesis and more specifically on early skeletal development of the Antarctic fish, N. coriiceps. We hypothesize that fish embryos raised at the higher temperature of +4°C will develop faster compared to embryos raised at the normal water temperature of about -1°C. In addition, we hypothesize that elevated temperature will result in asynchronous and abnormal development of various skeletal elements in embryos compared to control embryos raised at normal temperature. For this study, reproductive adult Notothenia coriiceps were collected around the Antarctic Peninsula in 2014 and 2016. Half of the embryos obtained by in vitro fertilization were raised at +4°C and composed the “heated” group, while the other half were raised at natural temperature between -1 and 0°C and formed the “control” group. We collected embryos at regular intervals during the first four months of development, fixed them and preserved them in 80% ethanol. The development and morphology of skeletal elements was recorded with a numbering system and results showed that the “heated” embryos had a faster embryonic and skeletal development compared to the “control” embryos, confirming our hypotheses. Our results therefore indicate that elevated water temperatures impact the normal skeletal development of the Antarctic fish larvae and could alter their survival if global warming predictions prove to be accurate. Additionally, there is asynchronous development between the cranial facial skeletal features and the axial skeleton among the two sample groups that could lead to later development issues

Short Range Sonic Hedgehog Signaling Promotes Heterotypic Cell Interactions Underlying Branching Morphogenesis of the Zebrafish Fin Skeleton

Presenter(s): Joshua Braunstein – Biology

Faculty Mentor(s): Kryn Stankunas, Scott Stewart

Poster 83

Research Area: Developmental Biology

Funding: ESPRIT
IMB Summer Scholarship Award
Alden Award

Zebrafish remarkably regenerate severed fins, perfectly restoring their original size and branched skeletal pattern. Sonic hedgehog a (Shha)-expressing epidermal cells mediate ray branching during regeneration by guiding localization of the pre-osteoblasts (pObs) while migrating and splitting into two populations. However, mechanisms of shha induction, the splitting of shha+ epidermal cells, and the mechanisms underlying epidermal to pObs interactions remain unresolved. Towards answering these questions, we explored if Hh/Smo signaling and epidermal dynamics also underlie developmental ray branching. We found that shha is expressed initially in basal epidermal cells along the entire length of forming fin bones in juvenile fish. As bones progressively mature, shha becomes distally restricted to epidermal cells neighboring Runx2+ pObs. We used TgBAC(ptch2:Kaede) fish and photoconversion to show Hh/Smo signaling is restricted to these pObs and immediately adjacent epidermal cells. shha+ epidermal cells split into two groups immediately preceding ray branching. By live imaging, we found these basal epidermal cells migrate distally over the pObs, cease Hh/Smo signaling, and are then shed. Small molecule inhibition of Hh/Smo using BMS-833923 increased epidermal migration speed, suggesting Hh/Smo signaling typically restricts the rate of migration by adhering epidermal cells to the pObs. Additional small molecule trials show the pathway is largely dedicated to ray branching during fin development. We conclude that instructive shha+ epidermal movements and Shh/Smo-promoted adhesion between epidermal cells and pObs direct branching morphogenesis to pattern the fin skeleton during both development and regeneration.