Lmx1a drives Cux2 expression in the cortical hem through activation of a conserved intronic enhancer.

During neocortical development, neurons are produced by a diverse pool of neural progenitors. A subset of progenitors express the gene and are fate restricted to produce certain neuronal subtypes; however, the upstream pathways that specify these progenitor fates remain unknown. To uncover the transcriptional networks that regulate expression in the forebrain, we characterized a conserved enhancer that recapitulates expression specifically in the cortical hem.

The Dorsal Wave of Neocortical Oligodendrogenesis Begins Embryonically and Requires Multiple Sources of Sonic Hedgehog.

Neural progenitor cells in the developing dorsal forebrain give rise to excitatory neurons, astrocytes, and oligodendrocytes for the neocortex. While we are starting to gain a better understanding about the mechanisms that direct the formation of neocortical neurons and astrocytes, far less is known about the molecular mechanisms that instruct dorsal forebrain progenitors to make oligodendrocytes. In this study, we show that Sonic hedgehog (Shh) signaling is required in dorsal progenitors for their late embryonic transition to oligodendrogenesis.

Lineage Tracing Using Cux2-Cre and Cux2-CreERT2 Mice.

Using genetic fate-mapping with Cux2-Cre and Cux2-CreERT2 mice we demonstrated that the neocortical ventricular zone (VZ) contains radial glial cells (RGCs) with restricted fate potentials (Franco et al., 2012). Using the same mouse lines, Guo et al.

9-Phenanthrol and flufenamic acid inhibit calcium oscillations in HL-1 mouse cardiomyocytes.

It is well established that intracellular calcium ([Ca2+]i) controls the inotropic state of the myocardium, and evidence mounts that a "Ca2+ clock" controls the chronotropic state of the heart. Recent findings describe a calcium-activated nonselective cation channel (NSCCa) in various cardiac preparations sharing hallmark characteristics of the transient receptor potential melastatin 4 (TRPM4). TRPM4 is functionally expressed throughout the heart and has been implicated as a NSCCa that mediates membrane depolarization.

Expression of calcium transport proteins in the extraembryonic membranes of a viviparous snake, Virginia striatula.

Yolk is the primary source of calcium for embryonic growth and development for most squamates, irrespective of mode of parity. The calcified eggshell is a secondary source for embryonic calcium in all oviparous eggs, but this structure is lost in viviparous lineages. Virginia striatula is a viviparous snake in which embryos obtain calcium from both yolk and placental transport of uterine calcium secretions.

Developmental expression of calcium transport proteins in extraembryonic membranes of oviparous and viviparous Zootoca vivipara (Lacertilia, Lacertidae).

The eggshell of oviparous lizards is a significant source of calcium for embryos, whereas the eggshell of viviparous lizards, when present, contains little calcium. In view of the potential cost to embryonic nutrition occasioned by the loss of eggshell calcium, the large number of independent origins of viviparity among lizards is surprising. Concomitant evolution of viviparity and calcium placentotrophy would ameliorate the loss of eggshell calcium, but a mechanism linking these events has yet to be discovered.

Embryonic mobilization of calcium in a viviparous reptile: evidence for a novel pattern of placental calcium secretion.

Yolk reserves supply the majority of embryonic nutrition in squamate reptiles, including calcium. Embryos of oviparous squamates exploit the eggshell for supplemental calcium, while embryos of viviparous species may receive additional calcium via the placenta. Developmental uptake of calcium in oviparous snakes increases during the interval of greatest embryonic growth (stage 35 to parturition).

Maternal provision and embryonic uptake of calcium in an oviparous and a placentotrophic viviparous Australian lizard (Lacertilia: Scincidae).

Embryos of oviparous lizards have two sources of calcium for embryonic development: 1) calcium that accumulates in yolk during vitellogenesis, and 2) calcium carbonate deposited in the eggshell from oviductal secretions. Eggs of viviparous lizards lack a calcified eggshell and calcium secreted by the uterus is delivered to the embryo across a placenta. Whereas oviparous lizard embryos recover calcium from the eggshell during late developmental growth stages, viviparous embryos have a lengthy intimate association with the uterus and the potential for an extended interval of placental calcium transfer.