: Huntington's disease is caused by a pathologically long (>35) CAG repeat located in the first exon of the Huntingtin gene (HTT). While pathologically expanded CAG repeats are the focus of extensive investigations, non-pathogenic CAG tracts in protein-coding genes are less well characterized. Here, we investigated the function and evolution of the physiological CAG tract in the HTT gene. We show that the poly-glutamine (polyQ) tract encoded by CAGs in the huntingtin protein (HTT) is under purifying selection and subjected to stronger selective pressures than CAG-encoded polyQ tracts in other proteins. For natural selection to operate, the polyQ must perform a function. By combining genome-edited mouse embryonic stem cells and cell assays, we show that small variations in HTT polyQ lengths significantly correlate with cells' neurogenic potential and with changes in the gene transcription network governing neuronal function. We conclude that during evolution natural selection promotes the conservation and purity of the CAG-encoded polyQ tract and that small increases in its physiological length influence neural functions of HTT. We propose that these changes in HTT polyQ length contribute to evolutionary fitness including potentially to the development of a more complex nervous system.

The evolutionary history of the polyQ tract in huntingtin sheds light on its functional pro-neural activities / R. Iennaco, G. Formenti, C. Trovesi, R.L. Rossi, C. Zuccato, T. Lischetti, V.D. Bocchi, A. Scolz, C. Martínez-Labarga, O. Rickards, M. Pacifico, A. Crottini, A.P. Møller, R.Z. Chen, T.F. Vogt, G. Pavesi, D.S. Horner, N. Saino, E. Cattaneo. - In: CELL DEATH AND DIFFERENTIATION. - ISSN 1476-5403. - 29:2(2022 Jan), pp. 293-305. [10.1038/s41418-021-00914-9]

The evolutionary history of the polyQ tract in huntingtin sheds light on its functional pro-neural activities

Iennaco, Raffaele;Formenti, Giulio;Trovesi, Camilla;Zuccato, Chiara;Lischetti, Tiziana;Bocchi, Vittoria Dickinson;Scolz, Andrea;Crottini, Angelica;Pavesi, Giulio;Horner, David Stephen;Saino, Nicola;Cattaneo, Elena
2022-01

Abstract

: Huntington's disease is caused by a pathologically long (>35) CAG repeat located in the first exon of the Huntingtin gene (HTT). While pathologically expanded CAG repeats are the focus of extensive investigations, non-pathogenic CAG tracts in protein-coding genes are less well characterized. Here, we investigated the function and evolution of the physiological CAG tract in the HTT gene. We show that the poly-glutamine (polyQ) tract encoded by CAGs in the huntingtin protein (HTT) is under purifying selection and subjected to stronger selective pressures than CAG-encoded polyQ tracts in other proteins. For natural selection to operate, the polyQ must perform a function. By combining genome-edited mouse embryonic stem cells and cell assays, we show that small variations in HTT polyQ lengths significantly correlate with cells' neurogenic potential and with changes in the gene transcription network governing neuronal function. We conclude that during evolution natural selection promotes the conservation and purity of the CAG-encoded polyQ tract and that small increases in its physiological length influence neural functions of HTT. We propose that these changes in HTT polyQ length contribute to evolutionary fitness including potentially to the development of a more complex nervous system.
Settore BIO/14 - Farmacologia
CELL DEATH AND DIFFERENTIATION
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/2434/917893
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