Mouse homologues of the human AZF candidate gene RBM are expressed in spermatogonia and spermatids, and map to a Y chromosome deletion interval associated with a high incidence of sperm abnormalities

An RNA-binding motif (RBM) gene family has been identified on the human Y chromosome that maps to the same deletion interval as the 'azoospermia factor' (AZF). We have identified the homologous gene family (Rbm) on the mouse Y with a view to investigating the proposal that this gene family plays a role in spermatogenesis. At least 25 and probably >50 copies of Rbm are present on the mouse Y chromosome short arm located between Sry and the centromere. As in the human, a role in spermatogenesis is indicated by a germ cell-specific pattern of expression in the testis, but there are distinct differences in the pattern of expression between the two species. Mice carrying the deletion Yd1, that maps to the proximal Y short arm, are female due to a position effect resulting in non-expression of Sry ; sex-reversing such mice with an Sry transgene produces males with a high incidence of abnormal sperm, making this the third deletion interval on the mouse Y that affects some aspect of spermatogenesis. Most of the copies of Rbm map to this deletion interval, and the Yd1males have markedly reduced Rbm expression, suggesting that RBM deficiency may be responsible for, or contribute to, the abnormal sperm development. In man, deletion of the functional copies of RBM is associated with meiotic arrest rather than sperm anomalies; however, the different effects of deletion are consistent with the differences in expression between the two species.      

Distribution of mutations in the PEX gene in families with X-linked hypophosphataemic rickets (HYP)

Mutations in the PEX gene at Xp22.1 (phosphate-regulating gene with homologies to endopeptidases, on the X-chromosome), are responsible for X-linked hypophosphataemic rickets (HYP). Homology of PEX to the M13 family of Zn2+ metallopeptidases which include neprilysin (NEP) as prototype, has raised important questions regarding PEX function at the molecular level. The aim of this study was to analyse 99 HYP families for PEX gene mutations, and to correlate predicted changes in the protein structure with Zn2+ metallopeptidase gene function. Primers flanking 22 characterised exons were used to amplify DNA by PCR, and SSCP was then used to screen for mutations. Deletions, insertions, nonsense mutations, stop codons and splice mutations occurred in 83% of families screened for in all 22 exons, and 51% of a separate set of families screened in 17 PEX gene exons. Missense mutations in four regions of the gene were informative regarding function, with one mutation in the Zn2+-binding site predicted to alter substrate enzyme interaction and catalysis. Computer analysis of the remaining mutations predicted changes in secondary structure, N-glycosylation, protein phosphorylation and catalytic site molecular structure. The wide range of mutations that align with regions required for protease activity in NEP suggests that PEX also functions as a protease, and may act by processing factor(s) involved in bone mineral metabolism.      

VIOLENT BEHAVIOUR IN PYSCHIATRIC INPATIENTS

A study of violent behaviour among psychiatric inpatients in a large general hospital is presented. Over the study period of one year a total of 36 incidents of violence involving 26 patients were recorded. Schizophrenia was the most common diagnosis among assailants. Fellow patients were the main victims. Incidence of serious violence was low. Most incidents occurred in the night hours, from inmates of acute wards and mostly without any provocation.KEY WORDS: Violent behaviour, Psychiatric patients     

DNA immunization: mechanistic studies

DNA immunization works, as has been amply demonstrated in a variety of microbial and tumor models. However, the mechanisms which underpin its success remain unclear. Using intramuscular delivery of DNA, we wish to precisely define how DNA-encoded antigens induce CD8+ T-cells (most cytotoxic T-cells; CTL), CD4+ T-cells (mostly helper cells) and antibodies; and to use the accrued knowledge to rationally manipulate DNA vaccines, thus enabling us to optimize each of the above three types of immune response. We consider it likely that different mechanisms operate in each case. We have designed a DNA vaccine which induces CTL, but not antibodies. We will present evidence that CTL are induced by endogenously-synthesized protein, not by protein released from cells; and that in the absence of release of intact protein, antibodies are not induced, while CTL induction remains strong. We have used plasmid-encoded minigenes and have found that these short sequences also induce CTL; this, too, argues that CTL are induced by antigens presented following endogenous synthesis. We are attempting to determine how antigens are released from transfected cells, to interact with B-cells and induce antibodies, and are currently evaluating the CD4 responses induced by DNA vaccines.     

Myocarditis,Microbes and Autoimmunity

Acute and chronic myocarditis can be caused by a number of infectious agents, including viruses, bacteria and protozoa. These diseases are refractory to treatment, and the development of rational therapies will require a detailed understanding of the mechanisms that underlie the pathological inflammatory responses. Here, we review three infectious myocarditides that, despite the dissimilarity of the microorganisms, share several common features: (i) the microbes replicate in the heart; but (ii) are difficult to isolate, in infectious form, during chronic disease; (iii) autoreactive antibodies and T cells specific for cardiac antigens have been identified in infected animals; and (iv) these autoreactive responses have been proposed as the main effectors of cell death, and myocardial damage. We critically evaluate the data, and we suggest that the findings can be reconciled without invoking autoimmunity as an effector mechanism. Alternative hypotheses to explain the tissue destruction are proposed.     

The natural history of a genetic subtype of arrhythmogenic right ventricular cardiomyopathy caused by a p.S358L mutation in TMEM43

To determine the phenotype and natural history of a founder genetic subtype of autosomal dominant arrhythmogenic right ventricular cardiomyopathy (ARVC) caused by a p.S358L mutation in TMEM43. The age of onset of cardiac symptoms, clinical events and test abnormalities were studied in 412 subjects (258 affected and 154 unaffected), all of which occurred in affected males significantly earlier and more often than unaffected males. Affected males were hospitalized four times more often than affected females (p ≤ 0.0001) and died younger (p ≤ 0.001). The temporal sequence from symptoms onset to death was prolonged in affected females by 1–2 decades. The most prevalent electrocardiogram (ECG) manifestation was poor R wave progression (PRWP), with affected males twice as likely to develop PRWP as affected females (p ≤ 0.05). Left ventricular enlargement (LVE) occurred in 43% of affected subjects, with 11% fulfilling criteria for dilated cardiomyopathy. Ventricular ectopy on Holter monitor was common and occurred early: the most diagnostically useful clinical test. No symptom or test could rule out diagnosis. This ARVC subtype is a sex‐influenced lethal arrhythmogenic cardiomyopathy, with a unique ECG finding, LV dilatation, heart failure and early death, where molecular pre‐symptomatic diagnosis has the greatest clinical utility.