Selective Cortical Layering Abnormalities and Behavioral Deficits in Cortex-Specific Pax6 Knock-Out Mice

Abstract

The transcription factor Pax6 has been implicated in neocortical neurogenesis in vertebrates, including humans. Analyses of the role of Pax6 in layer formation and cognitive abilities have been hampered by perinatal lethality of Pax6 mutants. Here, we generated viable mutants exhibiting timed, restricted inactivation of Pax6 during early and late cortical neurogenesis using Emx1-Cre and hGFAP-Cre lines, respectively. The disruption of Pax6 at the onset of neurogenesis using Emx1-Cre line resulted in premature cell cycle exit of early progenitors, increase of early born neuronal subsets located in the marginal zone and lower layers, and a nearly complete absence of upper layer neurons, especially in the rostral cortex. Furthermore, progenitors, which accumulated in the enlarged germinal neuroepithelium at the pallial/subpallial border in the Pax6 mutants, produced an excess of oligodendrocytes. The inactivation of Pax6 after generation of the lower neuronal layers using hGFAP-Cre line did not affect specification or numbers of late-born neurons, indicating that the severe reduction of upper layer neurons in Pax6 deficiency is mostly attributable to a depletion of the progenitor pool, available for late neurogenesis. We further show that Pax6 fl/fl ;Emx1-Cre mutants exhibited deficiencies in sensorimotor information integration, and both hippocampus-dependent short-term and neocortex-dependent long-term memory recall. Because a majority of the morphological and behavior disabilities of the Pax6 mutant mice parallel abnormalities reported for aniridia patients, a condition caused by PAX6 haploinsufficiency, the Pax6 conditional mutant mice generated here represent a valuable genetic tool to understand how the developmental cortical disruption can lead to a human behavior abnormality.

Epigenetic regulation by BAF (mSWI/SNF) chromatin remodeling complexes is indispensable for embryonic development

“…50,51 The following polyclonal (pAb) and monoclonal (mAb) primary antibodies used in this study were obtained from the indicated commercial sources: Brg1 rabbit pAb (Santa Cruz), Brg1 mouse mAb (Santa Cruz), Brm mouse mAb (BD Biosciences), Brm rabbit pAb (Abcam), BAF250 mouse mAb (Sigma), BAF170 rabbit pAb (Bethyl), BAF170 rabbit pAb (Sigma), BAF155 rabbit pAb (Santa Cruz), BAF155 mouse mAb (Santa Cruz), BAF60a mouse mAb (BD Biosciences), GAPDH rabbit pAb (Santa Cruz), ß-actin rabbit pAb (Sigma), and H3K27me3 rabbit pAb (Upstate). The utilized secondary antibodies included peroxidase-conjugated goat anti-rabbit IgG (1:10,000; Covance), peroxidase-conjugated goat anti-mouse IgG (1:5000; Covance), and Alexa 488-or Alexa 568-conjugated IgG (various species,1: 400; Molecular Probes).…”

Functional dissection of the paired domain of Pax6 reveals molecular mechanisms of coordinating neurogenesis and proliferation

“…Sey or conditional Pax6 deletion, which have normal numbers of apical, but increased numbers of basal, progenitors (Haubst et al, 2004;Tuoc et al, 2009). As a particularly high number of basal progenitors is characteristic of the ventral telencephalon, and because the transcription factors that are normally restricted there, such as Gsx1/2, Dlx1/2 and Olig2, spread into the dorsal telencephalon, i.e.…”

“…The transcription factor Pax6 acts as a master regulator in various tissues, including the developing CNS and eye (Hanson and Van Heyningen, 1995;Dohrmann et al, 2000;Kozmik, 2008;. Pax6 has been established as a key regulator of patterning, fate and proliferation and is required to achieve appropriate CNS and eye development (Hanson and Van Heyningen, 1995;Stoykova et al, 1996;Stoykova et al, 1997;Götz et al, 1998;Chapouton et al, 1999;Stoykova et al, 2000;Toresson et al, 2000;Yun et al, 2001;Estivill-Torrus et al, 2002;Heins et al, 2002;Haubst et al, 2004;Quinn et al, 2007;Sansom et al, 2009;Tuoc et al, 2009). In addition, Pax6 is sufficient to elicit eye formation (Altmann et al, 1997;Chow et al, 1999) and instruct neuron formation even from non-neurogenic glial cells (Heins et al, 2002;Berninger et al, 2007).…”

Area-specific temporal control of corticospinal motor neuron differentiation by COUP-TFI

“…The area-specific differences in neuronal fate and cytoarchitecture have been thought to result from late postmitotic events, e.g. selective postnatal pruning of axons (11), and premitotic events, such as the timing, rate, and duration of proliferation of precursors producing distinct projection neuron subtypes (12)(13)(14)(15)(16). As a striking illustration of such processes, CSMN are generated at a higher rate in the developing motor cortex than in sensory areas in mice (12), but the molecular mechanisms that control this area-specific differential production of CSMN are not known.…”