Loss of UCHL1 promotes age-related degenerative changes in the enteric nervous system.

UCHL1 (ubiquitin carboxyterminal hydrolase 1) is a deubiquitinating enzyme that is particularly abundant in neurons. From studies of a spontaneous mutation arising in a mouse line it is clear that loss of function of UCHL1 generates profound degenerative changes in the central nervous system, and it is likely that a proteolytic deficit contributes to the pathology. Here these effects were found to be recapitulated in mice in which the Uchl1 gene had been inactivated by homologous recombination. In addition to the previously documented neuropathology associated with loss of UCHL1 function, axonal swellings were detected in the striatum. In agreement with previously reported findings the loss of UCHL1 function was accompanied by perturbations in ubiquitin pools, but glutathione levels were also significantly depleted in the brains of the knockout mice, suggesting that oxidative defense mechanisms may be doubly compromised. To determine if, in addition to its role in the central nervous system, UCHL1 function is also required for homeostasis of the enteric nervous system the gastrointestinal tract was analyzed in UCHL1 knockout mice. The mice displayed functional changes and morphological changes in gut neurons that preceded degenerative changes in the brain. The changes were qualitatively and quantitatively similar to those observed in wild type mice of much greater age, and strongly resemble changes reported for elderly humans. UCHL1 knockout mice should therefore serve as a useful model of gut aging

Le FORUM, Vol. 39 No. 2

https://digitalcommons.library.umaine.edu/francoamericain_forum/1045/thumbnail.jp

Multiple Promoters and Alternative Splicing: Hoxa5 Transcriptional Complexity in the Mouse Embryo

The genomic organization of Hox clusters is fundamental for the precise spatio-temporal regulation and the function of each Hox gene, and hence for correct embryo patterning. Multiple overlapping transcriptional units exist at the Hoxa5 locus reflecting the complexity of Hox clustering: a major form of 1.8 kb corresponding to the two characterized exons of the gene and polyadenylated RNA species of 5.0, 9.5 and 11.0 kb. This transcriptional intricacy raises the question of the involvement of the larger transcripts in Hox function and regulation.We have undertaken the molecular characterization of the Hoxa5 larger transcripts. They initiate from two highly conserved distal promoters, one corresponding to the putative Hoxa6 promoter, and a second located nearby Hoxa7. Alternative splicing is also involved in the generation of the different transcripts. No functional polyadenylation sequence was found at the Hoxa6 locus and all larger transcripts use the polyadenylation site of the Hoxa5 gene. Some larger transcripts are potential Hoxa6/Hoxa5 bicistronic units. However, even though all transcripts could produce the genuine 270 a.a. HOXA5 protein, only the 1.8 kb form is translated into the protein, indicative of its essential role in Hoxa5 gene function. The Hoxa6 mutation disrupts the larger transcripts without major phenotypic impact on axial specification in their expression domain. However, Hoxa5-like skeletal anomalies are observed in Hoxa6 mutants and these defects can be explained by the loss of expression of the 1.8 kb transcript. Our data raise the possibility that the larger transcripts may be involved in Hoxa5 gene regulation.Our observation that the Hoxa5 larger transcripts possess a developmentally-regulated expression combined to the increasing sum of data on the role of long noncoding RNAs in transcriptional regulation suggest that the Hoxa5 larger transcripts may participate in the control of Hox gene expression

Identification of novel gene, TRAP1, using a replication-competent promoter-trap retrovirus in the mouse mammary gland.

Breast cancer remains one of the leading malignancies in women of the developed world despite the extra efforts that have been deployed in the past decade or so to the study of this disease. It is well known that the degree of aggressivity of the tumor is related to the stage of differentiation. Transformation of a cell having a high proliferation potential will lead to a more aggressive tumor than transformation of a more differentiated cell. For this reason it is important to have a good understanding of the process of mammary differentiation. The work in this thesis was directed at finding novel genes that are involved in the normal development of the breast with the hope that these may open new avenues for breast cancer therapies. The approach used was to look for genes that are expressed during breast development in the living mouse. A promoter-trap retrovirus containing on oncogene as the promoterless indicator gene was introduced locally in the mammary glands of pubescent female mice. Integration of proviruses near an active cellular promoter lead to the expression of the oncogene from a cellular promoter which was detected by the formation of a tumor. To identify genes that are specifically active during differentiation of the breast tissue we looked for the appearance of tumors after the animals were mated. Two promoter-trap retroviruses were tested. The first one (COPT) was replication deficient and although it did work in vitro it did not give a high enough level of infection to be used in vivo. The second virus (PyT) was replication competent and was found to be a more suitable promoter-trap to be used in vivo. This was demonstrated by the isolation of a novel murine gene named TRAP1

A conserved <i>HOTAIRM1-HOXA1</i> regulatory axis contributes early to neuronal differentiation

HOTAIRM1 is unlike most long non-coding RNAs in that its sequence is highly conserved across mammals. Such evolutionary conservation points to it having a role in key cellular processes. We previously reported that HOTAIRM1 is required to curb premature activation of downstream HOXA genes in a cell model recapitulating their sequential induction during development. We found that it regulates 3’ HOXA gene expression by a mechanism involving epigenetic and three-dimensional chromatin changes. Here we show that HOTAIRM1 participates in proper progression through the early stages of neuronal differentiation. We found that it can associate with the HOXA1 transcription factor and contributes to its downstream transcriptional program. Particularly, HOTAIRM1 affects the NANOG/POU5F1/SOX2 core pluripotency network maintaining an undifferentiated cell state. HOXA1 depletion similarly perturbed expression of these pluripotent factors, suggesting that HOTAIRM1 is a modulator of this transcription factor pathway. Also, given that binding of HOTAIRM1 to HOXA1 was observed in different cell types and species, our results point to this ribonucleoprotein complex as an integral part of a conserved HOTAIRM1-HOXA1 regulatory axis modulating the transition from a pluripotent to a differentiated neuronal state.</p

What if deliberately dying is an occupation?

In some legal and societal circumstances, people freely and capably plan, organize, and precipitate their own death. Drawing on published literature, we critically reflect on how deliberately ending one’s own life fits with the current definitions of the concept of occupation. Using an occupational science and occupational therapy theoretical reflection, we argue that deliberately dying can for some people be considered a purposeful and meaningful occupation. Implications for such an occupational therapy practice are discussed: attending to the occupational needs of specific groups of people, reconsidering definitions and conceptual work, advocating for occupational justice in ending life activities, reflecting on ethical conundrums around self-harm activities within the scope of practice, and exploring deliberate death as a purposeful and meaningful occupation. Because deliberately dying is something that some people do, in this article we aim to open a dialogue within the field of occupational science and occupational therapy about this sensitive and potentially controversial issue

Identification and characterization of Hedgehog modulator properties after functional coupling of Smoothened to G15.

The seven-transmembrane receptor Smoothened (Smo) transduces the signal initiated by Hedgehog (Hh) morphogen binding to the receptor Patched (Ptc). We have reinvestigated the pharmacological properties of reference molecules acting on the Hh pathway using various Hh responses and a novel functional assay based on the coexpression of Smo with the alpha subunit of the G15 protein in HEK293 cells. The measurement of inositol phosphate (IP) accumulation shows that Smo has constitutive activity, a response blocked by Ptc which indicates a functional Hh receptor complex. Interestingly, the antagonists cyclopamine, Cur61414, and SANT-1 display inverse agonist properties and the agonist SAG has no effect at the Smo-induced IP response, but converts Ptc-mediated inactive forms of Smo into active ones. An oncogenic Smo mutant does not mediate an increase in IP response, presumably reflecting its inability to reach the cell membrane. These studies identify novel properties of molecules displaying potential interest in the treatment of various cancers and brain diseases, and demonstrate that Smo is capable of signaling through G15