MYELINATION PROCESS DURING THE EMBRYOGENESIS OF LAGOSTOMUS MAXIMUS, A PRECOCIAL RODENT

JAIME VS, SCHMIDT AR, CORTASA SA, PROIETTO S, INSERRA PIF, LEOPARDO NP, CORSO MC; HALPERIN J; DORFMAN VB

Congreso; Reunion Anual de Biociencias 2021; 2021

Myelin is a protein synthesized by oligodendrocytes forming a multilaminarmembrane around the axons of the CNS. This membraneacts as an insulator increasing the speed of stimulus transmission.Myelination is a continuous process that begins when axons reacha diameter of approximately 1 μm and follows a structural sequencewith a caudo-rostral, dorso-ventral and center-to-periphery progressionwhich varies between species. The aim of this study was toanalyze the myelination process during the embryogenesis of theSouth America plains vizcacha, Lagostomus maximus, an hystricomorphrodent native from Argentina, and to compare it with this processin rat, mouse and guinea pig. Brains of 24 embryos, distributedbetween 51 embryonic days (e.d.) and 2 days postnatal, were usedand studied by Klüver-Barrera histological technique. The onset ofthe myelination process was observed around mid-pregnancy. Insidethe brain, the myelination process began around 72 e.d. up to118 e.d. in the cortex; at the same time, the myelination extendedtowards connection fibers beginning in the external cingulate at 106e.d. and gradually progressing towards the internal cingulate from112 e.d. onwards. At 124 e.d., the internal and external capsule,and optic chiasm were myelinated. After that, striosomes of the corpusstriatum and the fornix columns were myelinated at 133 e.d. Atbirth time (155 e.d.), all the intra-hemispheric white matter structureswere myelinated, but the inter-hemispheric connections of the corpuscallosum and the anterior commissure were not myelinated yet.These results show that both the onset of the myelination processand its progression during embryonic development are framed inthe precocial character of L. maximus. The onset of this processin vizcacha agreed with that in guinea pig, and was in contrast tothe postnatal onset in rat and mouse. Grant: Fundación CientíficaFelipe Fiorellino