engleski

Morphology, molecular phenotypes and spatiotemporal distribution of neurons in developing and adult human corpus callosum

The aim of this study was to analyze morphology, molecular phenotypes and developmental history of neurons in the human corpus callosum during prenatal and postnatal life. Postmortem brain tissue of 28 fetuses, 3 newborns, 4 infants and 8 adults, ranging from 15 postconception weeks (PCW) to 59 years of age, was histochemically processed for neuronal markers (MAP2, NeuN, NPY, parvalbumin, calretinin, calbindin, acetylcholinesterase-AChE). In addition to the neurons present in callosum-related developmental structures, such as midline sling, callosal septa and subcallosal zone, we found a hitherto undescribed heterogeneous neuronal population present within the corpus callosum trunk itself, most numerous during the fetal period and first postnatal year. This intracallosal population of neurons, seen first at 17th PCW, undergoes developmental changes, in morphology, chemical properties and spatial distribution, revealing at least two subpopulations: (i) transient fusiform (migratory-like) neurons (MAP2, calbindin and calretinin positive) which were observed mostly during second trimester and (ii) post-migratory, differentiated, phenotypically diverse neurons (MAP2, NPY, NeuN, AChE positive) present continuously during second half of gestation and in early postnatal period. Quantitative analysis showed that the number of intracallosal NeuN-positive neurons remains constant during the second half of gestation (from 22 PCW onwards), although they become “ diluted” due to the continued growth of the corpus callosum. At the same time, their morphology became more complex and diverse, reaching maximum in size and differentiation in the corpus callosum of newborn infant. During early postnatal years many intracallosal neurons remain in the corpus callosum, preserving size and morphology obtained during perinatal development. However, in the adult brain, intracallosal neurons were only sporadically found, mostly with shrunken body and without large dendritic staining, which indicates significant decrease in quantity during the late postnatal life. Thus, the intensive growth of the human corpus callosum during second half of gestation and early postnatal period is accompanied by transient but well developed and differentiated intracallosal neuronal population. We propose that, like the subplate neurons in developing frontal cortex, intracallosal neurons may have developmental role in guidance and stabilization of interhemispheric connectivity and later some transform into interstitial neurons, whilst their origin and fate remains to be elucidated

neuron-specific nuclear protein; fetal brain; telencephalic midline; interstitial neurons; callosal septa

nije evidentirano