Human brain has remarkably increased in size as well as acquired greater cognitive abilities compared to its nearest ancestor chimpanzee or gorilla. From the comparison between similar or larger size brains than human brain, it was noticed that human cortex has maximum number of neurons. Thus, it’s not size of the brain, but is the number of neurons; their packaging in the specialized neural circuits and final architecture of the brain might be the key for cognitive abilities and complexities of human brain. How human brain develops and integrates such large number of neurons in relatively small space, in a tight regulatory fashion, is the central question of the neurobiology.
Neurogenesis is a birth of neurons from neural stem cells or progenitors
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I have also reviewed maternal factors which sets platform for neurogenesis.
In the second chapter, I summarized advantage of using zebrafish as a model organism to study maternally inherited factors and neurogenesis. Then describe usefulness and weakness of transgenic zebrafish strain that has been developed in our lab previously. Further I focus on improvement of this strain to better understand process of neurogenesis and present a beautiful double transgenic
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Some of these lncRNAs could regulate gene expression and signaling events at various stages of brain development, including axogenesis and dendritogenesis. The forth chapter of this thesis is a story of one such novel lncRNA, named durga, arising from the 5’ end of kalirin a (kalrna), a key protein involved in axon and dendrite development, nerve growth and synaptic re-modeling. Over-expression of durga in the zebrafish embryo led to an increase in kalrna mRNA expression. The morphology of the neurons cultured from durga injected embryos had significantly fewer and shorter dendrites. Although durga has no apparent sequence homolog in mammals, based on gene synteny, it was found that a non-coding RNA arising from the 5′ end of the human Kalrn gene and expressed in the human neuronal cell line. So it is proposed that the zebrafish lncRNA durga maintains dendritic length and density through regulation of kalrna expression and this may have further implications in mammalian