Inborn errors of complex II--unusual human mitochondrial diseases.

The succinate dehydrogenase consists of only four subunits, all nuclearly encoded, and is part of both the respiratory chain and the Krebs cycle. Mutations in the four genes encoding the subunits of the mitochondrial respiratory chain succinate dehydrogenase have been recently reported in human and shown to be associated with a wide spectrum of clinical presentations. Although a comparatively rare deficiency in human, molecularly defined succinate dehydrogenase deficiency has already been found to cause encephalomyopathy in childhood, optic atrophy or tumor in adulthood. Because none of the typical housekeeping genes encoding this respiratory chain complex is known to present tissue-specific isoforms, the tissue-specific involvement represents a quite intriguing question, which is mostly addressed in this review. A differential impairment of electron flow through the respiratory chain, handling of oxygen, and/or metabolic blockade possibly associated with defects in the different subunits that can be advocated to account for tissue-specific involvement is discussed.     

Polypyrimidine Tract Binding Protein Prevents Activity of an Intronic Regulatory Element That Promotes Usage of a Composite 3��-Terminal Exon

Alternative splicing of 3′-terminal exons plays a critical role in gene expression by producing mRNA with distinct 3′-untranslated regions that regulate their fate and their expression. The Xenopus α-tropomyosin pre-mRNA possesses a composite internal/3′-terminal exon (exon 9A9′) that is differentially processed depending on the embryonic tissue. Exon 9A9′ is repressed in non-muscle tissue by the polypyrimidine tract binding protein, whereas it is selected as a 3′-terminal or internal exon in myotomal cells and adult striated muscles, respectively. We report here the identification of an intronic regulatory element, designated the upstream terminal exon enhancer (UTE), that is required for the specific usage of exon 9A9′ as a 3′-terminal exon in the myotome. We demonstrate that polypyrimidine tract binding protein prevents the activity of UTE in non-muscle cells, whereas a subclass of serine/arginine rich (SR) proteins promotes the selection of exon 9A9′ in a UTE-dependent way. Morpholino-targeted blocking of UTE in the embryo strongly reduced the inclusion of exon 9A9′ as a 3′-terminal exon in the endogenous mRNA, demonstrating the function of UTE under physiological circumstances. This strategy allowed us to reveal a splicing pathway that generates a mRNA with no in frame stop codon and whose steady-state level is translation-dependent. This result suggests that a non-stop decay mechanism participates in the strict control of the 3′-end processing of the α-tropomyosin pre-mRNA.     

Anther-specific,developmentally regulated expression of genes encoding a new class of proline-rich proteins in sunflower

We have used RNA gel blot analysis to demonstrate the anther-specific expression of three genes in sunflower. Expression of these genes was first detected shortly before flower opening, which occurs sequentially on the sunflower inflorescence, and continues during pollination. In contrast, these genes are not expressed (or only weakly expressed) in a male-sterile line in which anther development aborts. In situ hybridization experiments showed that these genes are only expressed in the single cell layer of the sunflower anther epidermis. In the case of one of these genes, which codes for an abundant mRNA, we report the peptide sequences deduced from the sequence of two similar but non identical cDNAs. These proteins contain a potential signal peptide and are characterized by the presence of a proline-rich region which reads KPSTPAPPPPPP(PP)K. Our results also suggest that several proline-rich proteins of unknown functions are specifically synthesized during the maturation of anthers in sunflower.     

Assignment by in situ hybridization of a fibroblast growth factor receptor gene to human chromosome band 10q26

Summary A 2.3-kb cDNA probe for the human bek fibroblast growth factor receptor was used to determine the chromosomal localization of the corresponding gene by in situ hybridization. The results show that this gene, a form of which is amplified in some poorly differentiated stomach cancers, is localized on chromosome region 10q26. The two previously identified fibroblast growth factor receptor genes are thus not on the same chromosome, as the related fig (fms-like gene) fibrovblast growth factor receptor gene has previously been mapped to human chromosome region 8p12.     

Lysosomal hydrolase activity in chorionic villi and embryonic cells in culture

Summary Fourteen lysosomal enzymes were compared in 20 cultured cell lines from chorionic biopsy and corresponding embryonic tissue after voluntary abortions. Enzymatic expression appears to be similar in cultured cells from both sources with some slightly higher levels for chorionic villi. We stress the importance of culturing chorionic villi especially in the case of enzymes (-L-iduronidase) or diseases (I cell disease) whose expression is unusual in fresh trophoblast tissue.     

Influence des héméropériodes très courtes sur la croissance de Lolium multiflorum,sa composition pigmentaire et l'ultrastructure chloroplastique

Summary We have described some characteristics of Lolium multiflorum cultivated under very short photoperiods (2 hours and 1 hour). The estimations of leaf growth were based on dry weight, surface measurements, and chlorophyll content. The pigment analyses were carried out by column chromatography; chloroplast ultrastructure was observed after chemical fixation.These measurements have permitted us to note a sharp drop in the growth curve of plants grown under different day-lengths: the limiting photoperiod lies between 1 hour and 2 hours of daily illumination.Pigment analyses and chloroplast ultrastructure observations show that there is a greater difference between plants cultivated under 1 hour and 2 hours of daily illumination than between plants cultivated under 2 hours and 12 hours.A decrease in day-length causes a deficit in the chlorophyll b content as well as a poor development of the grana.We have attempted to correlate these structural anomalies with the abnormal chlorophyll a/chlorophyll b ratio.     

The proposed 5′-nucleotidase inhibitor in human leukemic cells is an artefact

It is now well established that human lymphoblastoid cell lines showing immaturity characters display ecto-5′-nucleotidase activities lower than normal levels. A recent paper (Sun, A.S., Holland, J.F. and Ohnuma, T. (1983) Biochim. Biophys. Acta 762, 577–584) mentioned that this phenomenon resulted from the presence of a 5′-nucleotidase inhibitor in these cell lines. We demonstrate here that the use of 5′-[³H]AMP as a substrate, and inadequate analysis of the products formed, led them to a misinterpretation. [³H]Adenosine derived from 5′-[³H]AMP hydrolysis was further transformed into [³H]inosine by the adenosine deaminase activity of the leukemic cell lines tested; [³H]inosine was precipitated with the excess substrate and was not taken into account in the ecto-5′-nucleotidase determination, which led the authors to confuse this adenosine deaminase activity with a 5′-nucleotidase inhibitor. We did not observe 5′-nucleotidase inhibition by leukemic cell cytosol when convenient assay methods were used and showed that the presence of such an inhibitor remains to be established.     

Physical map of DNA from a new cauliflower mosaic virus strain

The restriction enzymes AluI, BamHI, BglII, EcoRI, HindIII, and SalI have been used to characterize and map a new cauliflower mosaic virus strain (Cabb-S). These fragments have been ordered by examining their overlapping regions after double enzymatic digestion. The single SalI cleavage site was chosen as the point of origin. We compare this strain with those already described.     

The importance of naturally attenuated SARS-CoV-2in the fight against COVID-19

The current SARS-CoV-2 pandemic is wreaking havoc throughout the world and has rapidly become a global health emergency. A central question concerning COVID-19 is why some individuals become sick and others not. Many have pointed already at variation in risk factors between individuals. However, the variable outcome of SARS-CoV-2 infections may, at least in part, be due also to differences between the viral subspecies with which individuals are infected. A more pertinent question is how we are to overcome the current pandemic. A vaccine against SARS-CoV-2 would offer significant relief, although vaccine developers have warned that design, testing and production of vaccines may take a year if not longer. Vaccines are based on a handful of different designs (i), but the earliest vaccines were based on the live, attenuated virus. As has been the case for other viruses during earlier pandemics, SARS-CoV-2 will mutate and may naturally attenuate over time (ii). What makes the current pandemic unique is that, thanks to state-of-the-art nucleic acid sequencing technologies, we can follow in detail how SARS-CoV-2 evolves while it spreads. We argue that knowledge of naturally emerging attenuated SARS-CoV-2 variants across the globe should be of key interest in our fight against the pandemic.