Cortical Cues Research Articles

Genetic Mechanisms Specifying Cortical Connectivity

Great neuroanatomists of the twentieth century recognized that the cerebral cortex of mammals is the single most complex structure of the central nervous system both in terms of neuronal diversity and connectivity. Understanding the cellular and molecular mechanisms specifying the afferent and efferent connectivity in the neocortex may seem like a daunting task. However, recent technical advances have greatly improved our ability to (1) profile gene expression of neuronal populations isolated based on their connectional properties, (2) manipulate gene expression in specific neuronal populations, and (3) visualize their axonal projections in vivo. These new tools are revolutionizing our ability to identify the molecular mechanisms patterning afferent and efferent cortical projections.

Area identity shifts in the early cerebral cortex of Emx2−/− mutant mice

The specification of area identities in the cerebral cortex is a complex process, primed by intrinsic cortical cues and refined after the arrival of afferent fibers from the thalamus. Little is known about the genetic control of the early steps of this process, but the distinctive expression pattern of the homeogene Emx2 in the developing cortex has prompted suggestions that it is critical in this context. We tested this hypothesis using Emx2 -/- mice. We found that the normal spectrum of cortical areal identities was encoded in these mutants, but areas with caudal-medial identities were reduced and those with anterior-lateral identities were relatively expanded in the cortex.

The role of microtubule dependent motors in centrosome movements and spindle pole organization during mitosis

Abstract In recent years, it has become clear that both plus and minus end directed motors are required for centrosome separation. In this review, we provide a speculative interpretation of results obtained in various systems. Plus end directed motors associated with centrosomes pushing on microtubules originating from the opposite centrosome may act in concert with plus end directed motors cross-linking anti-parallel microtubules to separate centrosomes in prophase. In addition, minus end directed motors present in the cell cortex could produce pulling forces on astral microtubules that contribute to centrosome separation and determine their final position in relation to cortical cues. Finally, we propose that centrosomes are maintained closely associated with the nuclear envelope during their migration through pulling forces applied on astral microtubules by minus end directed motors associated with the nuclear envelope. We also discuss the role of motors in spindle pole assembly and separation in the absence of centrosomes.