Triiodothyronine-Induced Shortening of Chromatin Repeat Length in Neurons Cultured in a Chemically Denned Medium

Abstract: At the time of terminal differentiation, mammalian cortical neurons undergo a dramatic change in the structural organization of their chromatin: the nucleosomal repeat length shortens from ∼200 base pairs in fetuses to a value of 165 base pairs after birth. These events occur several days after the end of neuronal proliferation. Previously, we reported that rat cortical neurons cultured in a very selective synthetic medium were not yet programmed to these events at the end of mitotic cycles. Herein, we report that addition of triiodothyronine to neuronal cultures induces a shortening of the chromatin repeat length comparable to the natural one. Copyright © 1987, Wiley Blackwell. A…

Rat CNS neurons are not yet programmed to shorten their chromatin repeat length at the end of fetal neurogenesis.

Neurons from rat fetal cerebral hemispheres were grown in a synthetic medium (Maat medium), as previously described, for different periods of time. The repeat length of their chromatin was determined by micrococcal nuclease digestion and compared with that of neurons isolated from postnatal rat brain of corresponding ages. In contrast to the in vivo situation, we found that neurons, dissociated at the 16th gestational day and cultured in vitro, did not undergo the shortening of their chromatin repeat, thus indicating that, at the end of their mitotic cycles, they are not yet programmed to this event. © 1986.

Cloning and analysis of cDNA for rat histone H1°

The Increase in Maternal Expression ofaxin1andaxin2Contribute to the Zebrafish MutantIchabodVentralized Phenotype

β-catenin is a central effector of the Wnt pathway and one of the players in Ca+-dependent cell-cell adhesion. While many wnts are present and expressed in vertebrates, only one β-catenin exists in the majority of the organisms. One intriguing exception is zebrafish that carries two genes for β-catenin. The maternal recessive mutation ichabod presents very low levels of β-catenin2 that in turn affects dorsal axis formation, suggesting that β-catenin1 is incapable to compensate for β-catenin2 loss and raising the question of whether these two β-catenins may have differential roles during early axis specification. Here we identify a specific antibody that can discriminate selectively for β-ca…

Effects of triiodothyronine (T3) on differentiation of rat cortical neurons in primary cultures.

Some of the events which characterize neuronal terminal differentiation have been studied in rat cortical neurons cultured in a selective synthetic medium for a period which corresponds to terminal brain maturation in vivo. In particular, we have studied the effect of T3 on the synthesis of nuclear proteins and the expression of the mRNAs which encode different variants of T3 nuclear receptors (c erb A proteins). We have shown that: a) T3 stimulates the turnover of nuclear proteins, with a more evident effect on the non-histone component; b) for the whole lifespan of cultures the predominant form of c erb Aα mRNA is the α2 variant (which encodes a protein unable to bind T3); whatever the fu…

The dynamic properties of neuronal chromatin are modulated by triiodothyronine.

The effect of triiodothyronine (T3) on the rate of synthesis of nuclear proteins was studied during terminal differentiation of rat cortical neurons cultured in a serum-free medium. To this aim total and acid soluble nuclear proteins were analyzed by different electrophoretic techniques. Our results show that: 1) during maturation in vitro, neuronal nuclei undergo a dramatic change in the rate at which different classes of histones and high mobility group (HMG) proteins are synthesized; the synthetic activity, measured as incorporation of radioactive precursors into nuclear proteins, slows indeed down with age: especially evident is the decrease in core histones synthesis; at day 15, on the…

Expression of synapsin I gene in primary cultures of differentiating rat cortical neurons

Synapsin I is a neuron-specific protein which is present in two isoforms, Ia and Ib. In the last few years this protein has been demonstrated to play a central role in the regulation of neurotransmitter release and synaptic plasticity. In this paper the developmental expression of this protein has been investigated in primary neuronal cultures from fetal rat brain cortices. The presence of thyroid hormone in the culture medium stimulates an early expression of the protein without exerting any effect at the level of mRNA transcription and accumulation. These observations implicate a T3-dependent regulation of this neuron-specific gene at the level of mRNA translation. © 1995 Plenum Publishin…