Evolutionary Perspective and Expression Analysis of Intronless Genes Highlight the Conservation of Their Regulatory Role.

Autor:	Aviña-Padilla K; Instituto de Neurobiología, Universidad Nacional Autónoma de México, Querétaro, Mexico.; Centro de Investigacioìn y de Estudios Avanzados del IPN, Unidad Irapuato, Guanajuato, Mexico., Ramírez-Rafael JA; Centro de Física Aplicada y Tecnología Avanzada, Universidad Nacional Autónoma de México, Querétaro, Mexico., Herrera-Oropeza GE; Instituto de Neurobiología, Universidad Nacional Autónoma de México, Querétaro, Mexico.; Centre for Developmental Neurobiology, Institute of Psychiatry, Psychology, and Neuroscience, King's College London, London, United Kingdom., Muley VY; Instituto de Neurobiología, Universidad Nacional Autónoma de México, Querétaro, Mexico., Valdivia DI; Centro de Investigacioìn y de Estudios Avanzados del IPN, Unidad Irapuato, Guanajuato, Mexico., Díaz-Valenzuela E; Centro de Investigacioìn y de Estudios Avanzados del IPN, Unidad Irapuato, Guanajuato, Mexico., García-García A; Centro de Física Aplicada y Tecnología Avanzada, Universidad Nacional Autónoma de México, Querétaro, Mexico., Varela-Echavarría A; Instituto de Neurobiología, Universidad Nacional Autónoma de México, Querétaro, Mexico., Hernández-Rosales M; Centro de Investigacioìn y de Estudios Avanzados del IPN, Unidad Irapuato, Guanajuato, Mexico.
Jazyk:	angličtina
Zdroj:	Frontiers in genetics [Front Genet] 2021 Jul 09; Vol. 12, pp. 654256. Date of Electronic Publication: 2021 Jul 09 (Print Publication: 2021).
DOI:	10.3389/fgene.2021.654256
Abstrakt:	The structure of eukaryotic genes is generally a combination of exons interrupted by intragenic non-coding DNA regions (introns) removed by RNA splicing to generate the mature mRNA. A fraction of genes, however, comprise a single coding exon with introns in their untranslated regions or are intronless genes (IGs), lacking introns entirely. The latter code for essential proteins involved in development, growth, and cell proliferation and their expression has been proposed to be highly specialized for neuro-specific functions and linked to cancer, neuropathies, and developmental disorders. The abundant presence of introns in eukaryotic genomes is pivotal for the precise control of gene expression. Notwithstanding, IGs exempting splicing events entail a higher transcriptional fidelity, making them even more valuable for regulatory roles. This work aimed to infer the functional role and evolutionary history of IGs centered on the mouse genome. IGs consist of a subgroup of genes with one exon including coding genes, non-coding genes, and pseudogenes, which conform approximately 6% of a total of 21,527 genes. To understand their prevalence, biological relevance, and evolution, we identified and studied 1,116 IG functional proteins validating their differential expression in transcriptomic data of embryonic mouse telencephalon. Our results showed that overall expression levels of IGs are lower than those of MEGs. However, strongly up-regulated IGs include transcription factors (TFs) such as the class 3 of POU (HMG Box), Neurog1, Olig1 , and BHLHe22, BHLHe23 , among other essential genes including the β-cluster of protocadherins. Most striking was the finding that IG-encoded BHLH TFs fit the criteria to be classified as microproteins. Finally, predicted protein orthologs in other six genomes confirmed high conservation of IGs associated with regulating neural processes and with chromatin organization and epigenetic regulation in Vertebrata . Moreover, this study highlights that IGs are essential modulators of regulatory processes, such as the Wnt signaling pathway and biological processes as pivotal as sensory organ developing at a transcriptional and post-translational level. Overall, our results suggest that IG proteins have specialized, prevalent, and unique biological roles and that functional divergence between IGs and MEGs is likely to be the result of specific evolutionary constraints. Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. (Copyright © 2021 Aviña-Padilla, Ramírez-Rafael, Herrera-Oropeza, Muley, Valdivia, Díaz-Valenzuela, García-García, Varela-Echavarría and Hernández-Rosales.)
Databáze:	MEDLINE
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