CNKSR2: A new player in cerebral hemisphere formation in the chick forebrain

Work done in the lab of Prof. Jonaki Sen at the Department of Biological Sciences and Bioengineering (BSBE), Indian Institute of Technology Kanpur (IITK).

About author

Ms Niveda Udaykumar is a PhD student in the laboratory of Prof. Jonaki Sen in the Department of Biological Sciences and Bioengineering (BSBE), Indian Institute of Technology Kanpur. In her PhD, she has worked to identify new molecular players involved in the separation of the cerebral hemispheres and her work has been recently published in Development.

Ms Niveda holds a Master’s in Applied Microbiology from Vellore Institute of Technology (VIT), Tamil Nadu and a Bachelor’s in Microbiology, Chemistry and Zoology from St. Joseph’s College, Bangalore. She is currently looking forward to defending her thesis in March 2023 after which she will head to St. Jude Children’s Research Hospital, in Tennessee, USA for her Postdoctoral research.

Interview

How would you explain your research outcomes to the non-scientific community?

The work that is being carried out in our lab is to try and understand a very fundamental question regarding the brain: How do the two cerebral hemispheres form?

We use the developing chick forebrain as a model organism to study this process. In particular, we are interested in finding answers to the question: What regulates forebrain midline invagination, a very critical step of the formation of the brain hemispheres? If this process does not take place, then, a very devastating congenital brain disorder known as “Holoprosencephaly” occurs, whose exact aetiology is still unknown. Hence, it is important to study and understand the molecules/players that drive this midline invagination process.

In a previous study from our lab, we identified that retinoic acid (RA) produced from Vitamin A is a regulator of this midline invagination process. Also, the blocking/inhibition of RA signalling in the forebrain led to a holoprosencephaly-like phenotype. Since the mechanism through which RA regulates this process of midline invagination was unknown, we searched for other unidentified regulators.

In this regard, we found a gene known as CNKSR2 to be expressed in the exact domain of RA signalling in the chick forebrain. We manipulated RA signalling in the forebrain and found that the expression of CNKSR2 changed, therefore, we concluded that CNKSR2 is a novel downstream mediator of the RA signalling in the chick forebrain midline.

We removed CNKSR2 from the chick forebrain by RNA interference (RNAi) and found that its removal also led to a holoprosencephaly-like phenotype. Further investigation revealed that causes for invagination defects were due to changes in patterning and the dysregulation of another signalling pathway, the Ras/Raf/MEK pathway.

In all, we found that CNKSR2 functions as a downstream effector of RA signalling and modulates the levels of the Ras/Raf/MEK pathway for the proper patterning of the forebrain and subsequently the separation of the two hemispheres.

How do these findings contribute to your research area?

Our work reports for the first time that CNKSR2 is a downstream effector of RA signalling that is involved in chick forebrain morphogenesis and its removal leads to a holoprosencephaly-like phenotype. These findings, if extrapolated, may be useful to establish the role of CNKSR2 in the aetiology of holoprosencephaly in humans too.

“Our work reports for the first time that CNKSR2 is a downstream effector of RA signalling that is involved in chick forebrain morphogenesis “

What was the exciting moment during your research?

I would say that the most exciting moments came from the holoprosencephaly-like phenotype that we observed during the knockdown of CNKSR2 in the chick forebrain, and the induction of roof plate markers (patterning genes) such as Bmp7 ectopically in the lateral forebrain upon misexpression of mouse CNKSR2. These two results were highly unanticipated!

What do you hope to do next?

We feel that we are just starting to scratch the surface in understanding the process of midline invagination in the chick forebrain. We believe that this process is much more complex with the involvement of the overlying mesenchyme layer, cell adhesion molecules, cytoskeleton rearrangements, and the cross-talk of multiple essential signalling pathways such as BMP, WNT, and RA signalling in the chick forebrain. My colleagues are investigating each of these aspects to try and piece together the big-picture of the dorsal forebrain midline invagination.

Where do you seek scientific inspiration from?

I feel that scientific inspiration is all around us and science never fails to “wow” us. But, the best scientific inspiration comes from the results that are interesting and unexpected in moments of failure and despair.

How do you intend to help Indian science improve?

One of the major factors for me to enter this line of research is to return to India and teach Science to middle/ high school students. I feel that this would be a full circle where I can give back to the scientific community to inspire bright and innovative Indian students to take up Basic/ Applied Sciences and allow their ideas to come to fruition. I strongly believe that students who can think and generate out-of-the-box ideas can help in improving Indian science to the maximum.

Reference

Niveda Udaykumar, Mohd Ali Abbas Zaidi, Aishwarya Rai, Jonaki Sen; CNKSR2, a downstream mediator of retinoic acid signaling, modulates the Ras/Raf/MEK pathway to regulate patterning and invagination of the chick forebrain roof plate. Development 1 February 2023; 150 (3): dev200857. doi: https://doi.org/10.1242/dev.200857

Copy Editor

Anjali Mahilkar

Postdoctoral Fellow at University of Michigan

Anjali is an evolutionary biologist working as a postdoctoral researcher in the department of Ecology and Evolutionary Biology at University of Michigan, Ann Arbor. Her research interests mainly lie in understanding the relationship between natural selection, adaptation and drift in deciding the evolutionary fates of biological functions as well as of whole organisms. She has a PhD from IIT Bombay where her research focused on understanding the process of speciation. Anjali also has her Masters from IIT Kanpur and Bachelor’s from NIT Raipur. She also had short work stints at Dr. Reddy’s Institute of Life Science and at a Central University in Chhattisgarh. She is interested in science communication and volunteers for several organizations towards the same. Although not an avid reader, she likes to read fiction in her free time.

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