A cDNA encoding a protein that binds retinoic acid with high affinity has been cloned. The protein is homologous to the receptors for steroid hormones, thyroid hormones and vitamin D3, and appears to be a retinoic acid-inducible trans-acting enhancer factor, suggesting that the molecular mechanisms of the effect of retinoids (vitamin A) on embryonic development, differentiation and tumour cell growth are similar to those described for other members of this nuclear receptor family.

We have identified a unique case of acute promyelocytic leukaemia (APL) with a t(11;17) reciprocal chromosomal translocation involving the retinoic acid receptor alpha (RAR alpha) and a previously uncharacterized zinc finger gene. As a result of this translocation, mRNAs containing the coding sequences of the new gene, fused in‐frame either upstream of the RAR alpha B region or downstream from the unique A1 and A2 regions of the two major RAR alpha isoforms, are expressed from the rearranged alleles. The above gene, which we have termed PLZF (for promyelocytic leukaemia zinc finger), encodes a potential transcription factor containing nine zinc finger motifs related to the Drosophila gap gene Krüppel and is expressed as at least two isoforms which differ in the sequences encoding the N‐terminal region of the protein. Within the haematopoietic system the PLZF mRNAs were detected in the bone marrow, early myeloid cell lines and peripheral blood mononuclear cells, but not in lymphoid cell lines or tissues. In addition, the PLZF mRNA levels were down‐regulated in NB‐4 and HL‐60 promyelocytic cell lines in response to retinoic acid‐induced granulocytic differentiation and were very low in mature granulocytes. Our results demonstrate for the first time the association of a variant chromosomal translocation involving the RAR alpha gene with APL, further implicating the RAR alpha in leukaemogenesis and also suggesting an important role for PLZF as well as retinoic acid and its receptors in myeloid maturation.

We have previously described a human complementary DNA that encodes a novel protein which is homologous to members of the steroid/thyroid nuclear receptor multigene family. This novel protein (hap for hepatoma) exhibits strong homology with the human retinoic acid receptor (RAR) which has been recently characterized. To test the possibility that the hap protein might also be a retinoid receptor, a chimaeric receptor was created by replacing the putative DNA binding domain of hap with that of the human oestrogen receptor (ER). The resulting hap-ER chimaera was then tested for its ability to trans-activate an oestrogen-responsive reporter gene (vit-tk-CAT) in the presence of possible receptor ligands. Here we show that retinoic acid (RA) at physiological concentrations is effective in inducing the expression of this reporter gene by the hap-ER chimaeric receptor. This demonstrates the existence of two human retinoic acid receptors designated RAR-alpha and RAR-beta.

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Recent reports have demonstrated the presence of two isoforms of troponin I in the human fetal heart, namely, cardiac troponin I and slow skeletal muscle troponin I. Structural and physiological considerations indicate that these isoforms would confer differing contractile properties on the myocardium, particularly on the phosphorylation-mediated regulation of contractility by adrenergic agonists. We have investigated the developmental expression of these isoforms in the human heart from 9 weeks of gestation to 9 months of postnatal life, using Western blots revealed with troponin I antibodies to detect troponin protein isoforms and Northern blots to detect the corresponding mRNAs. The results show the following: 1) Slow skeletal muscle troponin I is the predominant isoform throughout fetal life. 2) After birth, the slow skeletal isoform is lost, with cardiac troponin I being the only isoform detectable by 9 months of postnatal development. 3) The protein isoforms and their corresponding mRNAs follow the same pattern of accumulation, suggesting that the transition in troponin expression is regulated at the level of gene transcription. The developmental transition in troponin I isoform content has implications for contractility of the fetal and postnatal myocardium. We further analyzed right and left ventricular muscle samples from 17 hearts in end-stage heart failure resulting from pulmonary hypertension, ischemic heart disease, or dilated cardiomyopathy. Cardiac troponin I mRNA remained abundant in each case, and slow skeletal muscle troponin I mRNA was not detectable in any of sample. We conclude that alterations in troponin I isoform content do not therefore contribute to the altered contractile characteristics of the adult failing ventricle.

EMBL accession nos X65653-X65656 (incl.) and X65658-X65668 (incl.) SRY is the Y chromosomal gene which determines testis formation during mammalian embryogenesis (1). This gene encodes a potential transcription factor with a DNA binding motif known as a HMG box (2). Four murine autosomal SRY-related genes have been described having high homology to the HMG box region of SRY (3). We have cloned additional members of this gene family from phylogenetically diverse organisms. cDNAs prepared from mouse or human RNAs or phage lysates from cDNA libraries (Xenopus oocyte (4) and Drosophila embryo (0-12 hr) (Stratagene)), were used as templates in the polymerase chain reaction (PCR), using degenerate oligonucleotide primers which corresponded to regions conserved in the known SRY and SRY-related amino-acid sequences (Figure 1). Sequencing of the cloned PCR products demonstrated that they were heterogeneous, with the clones falling into a few, distinct classes, mostly differing from those SRY-related clones previously described (3). All of the encoded proteins are more closely related to SRYthan to other HMG-box proteins, including the T-cell factor TCF-1 (5) and the product of the S.pombe mating type gene, Mc (6). The SRY

Background-Poor survival of grafted cells is a major factor hindering the therapeutic effect of cell transplantation; however, the causes of cell death remain unclear. We hypothesized that interleukin-1␤ (IL-1␤) might play a role in the acute inflammatory response and graft death after cell transplantation and that inhibition of IL-1␤ might improve graft survival. Methods and Results-14 C-labeled male skeletal muscle precursor cells were implanted into female mouse hearts by direct intramuscular injection. The amount of 14 C-label provides an estimate of the surviving cell number, whereas the amount of male-specific Smcy gene measured by polymerase chain reaction indicates the total (survivingϩproliferated) number of donor-derived cells. At 10 minutes after implantation, 44.8Ϯ2.4% of the grafted cells survived and this steadily decreased to 14.6Ϯ1.1% by 24 hours, and to 7.9Ϯ0.6% by 72 hours (nϭ6 in each point). Proliferation of the surviving cells, which began after 24 hours, resulted in an increase in the total cell number from 15.5Ϯ0.8% at 24 hours to 24.4Ϯ1.6% at 72 hours. Acute inflammation was prominent at 24 hours and was reduced by 72 hours, in parallel with IL-1␤ expression. Administration of anti-IL-1␤ antibody improved graft survival at both 24 (25.6Ϯ1.6%) and 72 hours (14.8Ϯ1.1%) and resulted in a 2-fold increase in the total cell number at 72 hours (45.8Ϯ2.4%). The effects of IL-1␤ inhibition corresponded with a reduced inflammatory response. Conclusion-IL-1␤ is involved in acute inflammation and graft death after direct intramyocardial cell transplantation.Targeted inhibition of IL-1␤ may be a useful strategy to improve graft survival.

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