Howard Hughes Medical Institute

About: Howard Hughes Medical Institute is a nonprofit organization based out in Chevy Chase, Maryland, United States. It is known for research contribution in the topics: Gene & RNA. The organization has 20371 authors who have published 34677 publications receiving 5247143 citations. The organization is also known as: HHMI & hhmi.org.

Requirement for Hippocampal CA3 NMDA Receptors in Associative Memory Recall

Abstract: Pattern completion, the ability to retrieve complete memories on the basis of incomplete sets of cues, is a crucial function of biological memory systems. The extensive recurrent connectivity of the CA3 area of hippocampus has led to suggestions that it might provide this function. We have tested this hypothesis by generating and analyzing a genetically engineered mouse strain in which the N-methyl-D-asparate (NMDA) receptor gene is ablated specifically in the CA3 pyramidal cells of adult mice. The mutant mice normally acquired and retrieved spatial reference memory in the Morris water maze, but they were impaired in retrieving this memory when presented with a fraction of the original cues. Similarly, hippocampal CA1 pyramidal cells in mutant mice displayed normal place-related activity in a full-cue environment but showed a reduction in activity upon partial cue removal. These results provide direct evidence for CA3 NMDA receptor involvement in associative memory recall.

Conversion of Xenopus ectoderm into neurons by NeuroD, a basic helix-loop-helix protein

Abstract: Basic helix-loop-helix (bHLH) proteins are instrumental in determining cell type during development. A bHLH protein, termed NeuroD, for neurogenic differentiation, has now been identified as a differentiation factor for neurogenesis because (i) it is expressed transiently in a subset of neurons in the central and peripheral nervous systems at the time of their terminal differentiation into mature neurons and (ii) ectopic expression of neuroD in Xenopus embryos causes premature differentiation of neuronal precursors. Furthermore, neuroD can convert presumptive epidermal cells into neurons and also act as a neuronal determination gene. However, unlike another previously identified proneural gene (XASH-3), neuroD seems competent to bypass the normal inhibitory influences that usually prevent neurogenesis in ventral and lateral ectoderm and is capable of converting most of the embryonic ectoderm into neurons. The data suggest that neuroD may participate in the terminal differentiation step during vertebrate neuronal development.

The promise of induced pluripotent stem cells in research and therapy

Abstract: The field of stem-cell biology has been catapulted forward by the startling development of reprogramming technology. The ability to restore pluripotency to somatic cells through the ectopic co-expression of reprogramming factors has created powerful new opportunities for modelling human diseases and offers hope for personalized regenerative cell therapies. While the field is racing ahead, some researchers are pausing to evaluate whether induced pluripotent stem cells are indeed the true equivalents of embryonic stem cells and whether subtle differences between these types of cell might affect their research applications and therapeutic potential.