CNNE Seminar Series

Date:   Friday, May 27, 2022
Time:   12:00PM (noon) – 1:00PM Shenzhen // 2:00PM – 3:00PM Brisbane
Zoom:  https://uqz.zoom.us/j/85335877802

12:00PM SZX / 2:00PM BNE             

Welcome & Introduction by Professor Pankaj Sah

12:05PM SZX / 2:05PM BNE             

Presentation – Mr Matthew Kenna, PhD student, Sah lab, QBI

Title: Harnessing new approaches to reveal the neural circuitry of memory.

Abstract: Elucidating the neural circuitry that underpins memory formation is critical to understanding how the brain adapts and stores information. Until recently, these circuitry investigations have mostly been limited to recording activity from a population of neurons during learning, or manipulating neural activity in a brain region and assessing the effect on memory expression. However, the use of activity-dependent inducible systems allows for the labelling of neurons that become active during a particular phase of learning, also known as “engram tagging”. From this, we can apply various techniques to reveal characteristics of the circuitry that are specific to memory formation. Using activity-dependent labelling in rodents, we have shown that the consolidation of fear memories involves a significant shift in neural activity towards layer 2/3 cells of the medial prefrontal cortex (mPFC). In addition, through ex vivo electrophysiology and whole-brain clearing approaches, we have shown that a prominent long-range connection of the consolidated fear engram is to the basolateral complex of the amygdala (BLA). Furthermore, examination of the local circuitry in the mPFC suggests a high level of inhibitory neurons being allocated into the fear engram, providing insight into the circuitry of fear memory. Finally, in vivo optogenetic activation of fear engram neurons in the mPFC during extinction learning (similar to exposure therapy in humans), prevents the acquisition of extinction memories, resulting in the persistence of fear-related behaviours. Taken together, when coupled with traditional techniques, activity-dependent systems can provide new insights into the circuitry underlying memory formation.

12:25PM SZX / 2:25PM BNE

Introduction by Professor HOU Shengtao

12:30PM SZX / 2:30PM BNE

Presentation – Dr HUANG Zengjin PhD, Research Scientist, Wei Chen lab,  Department of Biology, SUSTech

Title: Convergent Evolution of Clustered Protocadherin Isoforms Enables Conserved Antagonistic Functions in Vertebrates.

Abstract: Clustered Protocadherins have important functions in mammalian nervous system development and are encoded by three gene clusters termed α-, β-, and γ-Pcdh. Functional studies on α- and γ-Pcdh genes in mouse show that they are involved in neurite self-recognition analogous to Drosophila Dscam1. Less is known about the in vivo role of β-Pcdh characterized by significantly shorter truncated cytoplasmic domains. β- Pcdh are not present in Xenopus tropicalis and Danio rerio. However, distinct alternative splicing in specific γ gene clusters (γ1 cluster) in X. tropicalis and D. rerio can generate novel short cPcdh isoforms resembling mammalian β-isoforms. Complete loss of γ1-Pcdh in X. tropicalis and knock-down in D. rerio, cause wide spread and strong defects in the development of the embryonic nervous system. Furthermore, single axon tracing of retinal ganglion cells (RGCs) in X. tropicalis revealed that loss of γ1-Pcdh reduces the complexity and size of terminal axon arbors of RGCs, which can be rescued by expression of long but not short γ1-Pcdh isoforms in single RGCs. In contrast, knock- down of the shorter γ1 isoforms results in aberrant, more complex, and larger terminal arbors. Moreover, the short but not long isoforms of γ1- Pcdh are essential for terminal differentiation of retinal cone cells in X. tropicalis as well as D. rerio. Overall, our results demonstrate that the alternatively spliced shorter and longer γ1-Pcdh isoforms can have distinct and antagonistic functions. Therefore, cPcdh long and short isoforms, generated by species-specific mechanisms, likely represent a form of convergent evolution and indicates a functional specialization of truncated cPcdh isoforms.

12:45PM SZX / 2:45PM BNE            

Q&A session and discussion

1:00PM SZX / 3:00PM BNE

Seminar concludes