Thrombospondin binds to the surface of human osteosarcoma cells and mediates platelet-osteosarcoma cell interaction

We have previously shown that thrombospondin (TSP) is synthesized and secreted by human MG-63 osteosarcoma cells. In this study, the secretion and cell surface expression of TSP by two different human osteosarcoma cell lines (MG-63 and TE-85) as well as the involvement of TSP in the platelet-aggregating activity of these tumor cells were studied. Using a sandwich enzyme-linked immunosorbent assay, MG-63 cells secreted 3-fold as much TSP as TE-85 cells at 48 h (0.17 +/- 0.01 (SD) versus 0.06 +/- 0.006 micrograms/10(6) cells, P = 0.007). Binding of exogenous 125I-TSP to MG-63 and TE-85 cells in monolayer indicated that binding was time and concentration dependent, saturable, and inhibited by excess cold TSP. However, despite a similar affinity, MG-63 cells had 10-fold more TSP-binding sites than TE-85 cells (402,394 +/- 130,346 versus 36,748 +/- 7,708 TSP-binding sites/cell; P = 0.002). Similar binding differences of 125I-TSP were observed with both osteosarcoma cell lines in suspension. A fluorescence-activated cell-sorting analysis was used in conjunction with an anti-TSP polyclonal antibody, and binding of endogenous TSP to MG-63 and TE-85 cells in suspension was investigated. Addition of an anti-TSP antibody to MG-63 and TE-85 cells in suspension increased the mean fluorescence intensity 50-fold when compared to an irrelevant antibody. Moreover, the fluorescence intensity of MG-63 cells with an anti-TSP polyclonal antibody was increased by 40% when compared to TE-85 cells. Since TSP was expressed on the surface of osteosarcoma cells, the involvement of this glycoprotein in the platelet-aggregating activity of MG-63 and TE-85 cells was therefore investigated using an anti-TSP polyclonal antibody and two monoclonal antibodies (P10 and MA-II), the epitopes of which lie within the Mr 140,000 non-heparin-binding fragment and the Mr 25,000 heparin-binding fragment of TSP, respectively. Preincubation of MG-63 cells (1 x 10(6) cells/ml) with either an anti-TSP polyclonal antibody (100 micrograms/ml) or monoclonal antibody P10 (15 micrograms/ml) inhibited by 80% other platelet-aggregating activity of these tumor cells, while anti-TSP monoclonal antibody MA-II (15 micrograms/ml) had no effect. In sharp contrast, the anti-TSP polyclonal antibody (100 micrograms/ml) only exhibited a slight inhibitory effect on platelet aggregation induced by TE-85 cells when using a low concentration of tumor cells (0.6 x 10(6) cells/ml).(ABSTRACT TRUNCATED AT 400 WORDS)

Transcriptional interference between c-Jun and the glucocorticoid receptor: mutual inhibition of DNA binding due to direct protein-protein interaction

Glucocorticoids are potent inhibitors of collagenase induction by phorbol esters and inflammatory mediators. The target for this negative effect is the AP-1 site within the collagenase promoter, which also mediates its induction. Negative regulation is due to repression of AP-1 activity by the glucocorticoid receptor (GCR). While the GCR is a potent inhibitor of AP-1 activity (Jun/Fos), both c-Jun and c-Fos are potent repressors of GCR activity. In vitro experiments using purified GCR and c-Jun proteins suggest that mutual repression is due to direct interaction between the two. Direct interaction between GCR and either c-Jun or c-Fos is demonstrated by cross-linking and coimmunoprecipitation. These findings reveal a cross talk between two major signal transduction systems used to control gene transcription in response to extracellular stimuli, and a novel mechanism for transcriptional repression.

Regulatory elements of the pro-opiomelanocortin gene: pituitary specificity and glucocorticoid repression

A short 543-bp fragment o f the pro-opiomelanocortin gene is sufficient for pituitary-specific expression and, in the anterior pituitary gland, for repression of pro-opiomelanocortin transcription by glucocorticoids. Within this 5'-flanking fragment of the gene, multiple regulatory elements contribute to tissue-specific expression and a single glucocorticoid receptor binding site acts as a "negative glucocorticoid response element." The current model for glucocorticoid repression depends on the mutually exclusive binding of the glucocorticoid receptor and of a positive transcription factor, the chicken ovalbumin upstream promoter element transcription factor, to overlapping DNA sequences within the negative glucocorticoid response element.

Glucocorticoid receptor binding to a specific DNA sequence is required for hormone-dependent repression of pro-opiomelanocortin gene transcription

Glucocorticoids rapidly and specifically inhibit transcription of the pro-opiomelanocortin (POMC) gene in the anterior pituitary, thus offering a model for studying negative control of transcription in mammals. We have defined an element within the rat POMC gene 5'-flanking region that is required for glucocorticoid inhibition of POMC gene transcription in POMC-expressing pituitary tumor cells (AtT-20). This element contains an in vitro binding site for purified glucocorticoid receptor. Site-directed mutagenesis revealed that binding of the receptor to this site located at position base pair -63 is essential for glucocorticoid repression of transcription. Although related to the well-defined glucocorticoid response element (GRE) found in glucocorticoid-inducible genes, the DNA sequence of the POMC negative glucocorticoid response element (nGRE) differs significantly from the GRE consensus; this sequence divergence may result in different receptor-DNA interactions and may account at least in part for the opposite transcriptional properties of these elements. Hormone-dependent repression of POMC gene transcription may be due to binding of the receptor over a positive regulatory element of the promoter. Thus, repression may result from mutually exclusive binding of two DNA-binding proteins to overlapping DNA sequences.

Absence of a bleeding tendency in severe acquired von Willebrand's disease. The role of platelet von Willebrand factor in maintaining normal hemostasis

A 67-year-old male with a prolonged activated partial thromboplastin time (APTT) of 43 seconds (normal, 25-40 seconds) was found to have laboratory features of von Willebrand's disease and IgA myeloma but had a normal bleeding time and no bleeding tendency. Plasma Factor VIII coagulant activity (F.VIII:C) was 80 U/L (0.08 U/mL), Factor VIII antigen (F.VIII:Ag) 70 U/L (0.07 U/mL), and von Willebrand's factor antigen (vWF:Ag) 50 U/L (0.05 U/mL) and ristocetin cofactor (vWF:RiCoF) 10 U/L (0.10 U/mL). The platelet vWF:Ag level was normal, whereas both platelet lysate and plasma vWF high molecular weight multimers were decreased. Patient plasma had no inhibitory effect on either F.VIII:C or vWF:RiCoF. However, when patient plasma was incubated with normal plasma, crossed immunoelectrophoresis for vWF:Ag demonstrated the presence of immune complexes. Infusion of 1-desamino-8-D-arginine vasopressin led to a transient correction of the plasma vWF:Ag multimer pattern. The survival of all components of vWF/F.VIII was decreased, as also occurred after cryoprecipitate. The levels of plasma F.VIII/vWF increased as the IgA values decreased after chemotherapy, whereas the platelet high molecular weight multimers remained decreased. The data suggest that the plasma vWF/F.VIII deficiency results from complexing of the IgA myeloma protein with vWF, resulting in premature clearance of the vWF/F.VIII complex. The absence of clinical bleeding likely results from the combination of a normal platelet vWF:Ag level and persistence of intermediate molecular weight vWF multimers.

Validity of the Bioself 110 fertility indicator

The Bioself 110 (Bioself Canada, Inc., Montréal, Québec, Canada) is an electronic computerized thermometer designed to identify the fertile and infertile phases of the menstrual cycle. The purpose of this study was to evaluate the validity of the device by comparing it with a reference method, the Ovustick (Monoclonal Antibodies, Inc., Mountain View, CA) luteinizing hormone (LH) surge detection kit. The Bioself 110 identified the 6-day fertile period in 86.4% of 220 cycles studied and 5 fertile days in 93.2%. The Bioself 110 correctly identified the postovulatory infertile phase in 93.3% of 178 cycles. On average, the device identified 10.9 fertile days and 10.6 postovulatory "safe" days per cycle. It was concluded the device would be a useful aid to couples trying to conceive or prevent pregnancy.

Ventricles as a major site of atrial natriuretic factor synthesis and release in cardiomyopathic hamsters with heart failure

The aim of the present study was to correlate in cardiomyopathic hamsters with congestive heart failure the levels of atrial and ventricular atrial natriuretic factor (ANF) messenger RNA (mRNA) with immunoreactive ANF (IR-ANF) plasma levels and the relative amount of IR-ANF released by the whole heart versus isolated ventricles in the Langendorff preparation. High-performance liquid chromatography analysis of the forms of ANF present in plasma and in the Langendorff effluent of whole heart versus isolated ventricles was also performed. As previously found for cardiac IR-ANF, the levels of ANF mRNA decreased gradually in atria and increased in an analogous fashion in ventricles with the severity of congestive heart failure. Plasma IR-ANF levels (C-terminal) were more elevated in moderate than in severe congestive heart failure, as were the IR-ANF levels in the Langendorff effluent of the whole heart. On the contrary, the effluent of isolated ventricles from animals in severe heart failure yielded more IR-ANF than that from hamsters in moderate heart failure. Thus, while the isolated ventricles from controls contributed 35.8% of IR-ANF released by the whole heart, ventricles from hamsters in moderate heart failure contributed 17.5%, and those from hamsters in severe heart failure contributed 73.9%. These results indicate that atrial cardiocytes contribute more IR-ANF than their ventricular counterpart in moderate heart failure and that ventricles are a major source of plasma IR-ANF in severe heart failure. Analysis of IR-ANF from plasma and the Langendorff effluent from whole hearts and isolated ventricles revealed that the ventricles are the major source of the propeptide (and of its cleaved products) found in the circulation of cardiomyopathic hamsters. These results suggest that ANF synthesis and secretion do not increase conjointly in atria but do increase in ventricles during congestive heart failure.

Independent glucocorticoid induction and repression of two contiguous responsive genes

Specific DNA sequence elements which contain binding sites for the glucocorticoid receptor mediate the action of glucocorticoid hormones on gene transcription. In glucocorticoid-inducible genes, these glucocorticoid-responsive elements behave as hormone-inducible enhancers of transcription. We have taken advantage of the bovine papillomavirus (BPV) system to test the stringency of glucocorticoid regulation of transcription. BPV episomes were constructed to contain two hormone-regulated transcription units in close proximity; one transcription unit is under control of a glucocorticoid-inducible promoter (mouse mammary tumor virus) while the other is under control of a glucocorticoid-inhibited promoter (pro-opiomelanocortin). Glucocorticoids independently regulated transcription of the two physically linked transcription units, irrespective of their relative orientation and of their proximity on the BPV episomes. This result contrasts with the so-called position-independent activity of enhancers and suggests that the multicomponent organization of eucaryotic promoters restricts the action of hormone-responsive regulatory elements to a specific transcription unit, thus accounting for the stringency of hormonal regulation observed in vivo.

Acute promyelocytic leukemia associated with a paraprotein that reacts with leukemic cells

A 29-year-old woman developed acute promyelocytic leukemia during pregnancy. At diagnosis, immediately postpartum, she was found to have IgG kappa immunoglobulin on the surface of the leukemic cells as well as a monoclonal protein of IgG kappa specificity in her serum. These resolved with chemotherapy which induced a complete remission. Immunoglobulin gene rearrangement was not found in the leukemic cells, thus indicating that the blasts were not secreting the monoclonal protein. The authors believe that the patient had an autoantibody directed at myeloid cells which was amplified by the development of the leukemic process.

Atrial natriuretic factor in the impulse-conduction system of rat cardiac ventricles

A complex network of atrial natriuretic factor-producing cells has been delineated by biochemical and morphological techniques in the rat ventricular myocardium. The chordae tendineae spuriae (CTS; false tendons) contain ANF mRNA and the ANF propeptide (Asn 1-Tyr 126) as assessed by Northern blot analysis, high-pressure liquid chromatography and immunohisto- and -cytochemistry, using three different affinity-purified antibodies: monoclonal and polyclonal antibodies against C-terminal ANF (Arg 101-Tyr 126) and polyclonal antibodies against N-terminal ANF (Asp 11-Ala 37). Two types of cells harboring ANF-containing secretory granules constitute the CTS: the majority (Purkinje type I) have ultrastructural similarities with both atrial and classical Purkinje fibers. Purkinje type-II fibers resemble working ventricular cardiocytes. Both cell types harbor a large paranuclear Golgi complex. The subendocardial Purkinje network is also made up of these two cell types. In this location, Purkinje type-I fibers form cable-like structures while Purkinje type-II fibers are either located beneath the former or abut directly on the endocardium. The latter are not separated from adjacent working ventricular cardiocytes by connective tissue septa. Coronary arteries and arterioles, as in birds, are surrounded by a cushion of Purkinje type-II fibers which blend with the surrounding myocardium. These results indicate that, in the rat, the entire intraventricular conduction system is constituted of endocrine cells producing ANF.

Lung is an important source of atrial natriuretic factor in experimental cardiomyopathy

The regulation of water and electrolyte homeostasis is multifactorial and includes the heart and kidneys as important regulatory centers. Within the heart, a recently discovered hormone, atrial natriuretic factor (ANF), has been implicated in the maintenance of water and salt balance. Primarily found in mammalian atria, ANF has been detected in low amounts in several tissues, including lungs. A disorder of the ANF system has been demonstrated in genetically cardiomyopathic hamsters, a model for human congestive cardiomyopathy. Atrial ANF gene expression and storage are decreased during development of this disease, while paradoxically, circulating levels of ANF are increased. We have hypothesized that an extracardiac source may contribute to ANF production in these pathological conditions. In this paper we provide evidence that ANF synthesis is stimulated in the lungs of hamsters during development of cardiomyopathy as revealed by increased ANF mRNA and peptide levels. Furthermore, we show that ANF synthesized in lungs is secreted and has identical chromatographic and biological properties to circulating ANF. The increased production of ANF in lungs may be physiologically important in preventing pulmonary edema. Alternatively, during cardiac dysfunction, lungs may play a compensatory role by increasing their contribution to plasma ANF levels.

Tissue-specific activity of the pro-opiomelanocortin (POMC) gene and repression by glucocorticoids

The gene encoding pro-opiomelanocortin (POMC) is specifically expressed in two different cell types of the pituitary gland. We have defined the regulatory DNA sequences of the POMC gene that are responsible for this cell-specific expression. In addition, we have defined a regulatory element, located in the proximal region of the POMC promoter, that confers glucocorticoid repression in the anterior pituitary. Using DNA-mediated gene transfer into transgenic mice and tissue culture cells, the POMC regulatory sequences required for cell-specific expression and glucocorticoid repression were localized within a 543-bp fragment in the 5'-flanking region of the gene. Multiple regulatory elements that bind nuclear proteins are present within this region. In particular, a sequence that binds the glucocorticoid receptor and behaves as a "negative glucocorticoid response element" (nGRE) also binds nuclear proteins of the COUP (chicken ovalbumin upstream promoter) family of transcription factors. Thus, glucocorticoid repression of POMC transcription may result from the mutually exclusive binding of the glucocorticoid receptor and the COUP transcription factor to the POMC nGRE.

Glucocorticoid repression of pro-opiomelanocortin gene transcription

Transcription of the pro-opiomelanocortin (POMC) gene is repressed by glucocorticoids in the anterior pituitary gland. We have defined an element within the POMC promoter which is responsible for this regulatory feedback. This element, the "negative glucocorticoid response element" (nGRE), was localized in the proximal region of the POMC promoter and it contains a binding site for the glucocorticoid receptor. Receptor binding to the nGRE was correlated to hormone-dependent repression by using promoter mutagenesis. The nGRE was also shown to contain a binding site for a nuclear protein of the COUP family of transcription factors. Since the binding sites for COUP and the glucocorticoid receptor overlap, glucocorticoid-dependent repression of POMC transcription may result from mutually exclusive binding of these two nuclear transcription factors.

Pituitary-specific expression and glucocorticoid regulation of a proopiomelanocortin fusion gene in transgenic mice

The product of a single gene encoding proopiomelanocortin (POMC) is differentially processed to produce corticotropin and alpha-melanotropin in anterior and intermediate pituitary cells, respectively. Hormonal control of POMC gene transcription and of corticotropin or alpha-melanotropin release is also tissue-specific; for example, glucocorticoids specifically inhibit anterior but not intermediate pituitary POMC transcription. Outside the pituitary gland, very low levels of POMC mRNAs are present in brain, testes, ovaries, and placenta. We have used transgenic mice to identify POMC 5' flanking sequences that are sufficient for tissue-specific expression and glucocorticoid regulation in anterior and intermediate pituitary cells. Three lines of transgenic mice were established, each carrying 50-75 copies (per cell) of a chimeric rPOMCneo gene constituted of rat POMC promoter sequences and of bacterial neomycin-resistance coding sequence. High levels of rPOMCneo transcripts were detected in pituitaries of mice from all three lineages. In situ hybridization revealed that the ratio of intermediate to anterior pituitary transcripts was similar for the transgene and endogenous POMC mRNA. rPOMCneo transcripts were not detected in any other tissue except at very low levels in the testes in two transgenic lines. Endogenous mouse POMC mRNA increased in response to depletion of plasma glucocorticoids (adrenalectomy) and decreased after glucocorticoid treatment; rPOMCneo transcripts were altered to the same extent by these treatments in all three lines. Intermediate pituitary and testicular rPOMCneo transgene expression was not altered by these treatments. Thus, no more than 769 base pairs of the rat POMC promoter are required for pituitary-specific expression and for specific glucocorticoid inhibition of the POMC gene in the anterior pituitary.

Residual amounts of glycoprotein Ib concomitant with near-absence of glycoprotein IX in platelets of Bernard-Soulier patients

A study of the Bernard-Soulier syndrome in two unrelated families using different polyclonal antibodies in a sensitive immunoblot assay showed residual amounts of platelet membrane glycoprotein (GP) lb in the eight homozygotes, as well as the near-absence of GPlb beta and GPIX. The eight heterozygotes studied showed a double band pattern for GPlb and about half the normal level of GPlb beta and GPIX. Therefore, we conclude that the Bernard-Soulier syndrome is heterogeneous and is probably not due to gene deletions.

Atrial natriuretic factor (ANF) gene expression in the Brattleboro rat

Atrial natriuretic factor (ANF) is a 28-amino acid peptide hormone of cardiac origin. It has natriuretic, diuretic and vasorelaxant properties and inhibits several cardiovascular modulators. Because of the possible effects of arginine vasopressin (AVP) on ANF secretion, we have investigated ANF gene expression in Brattleboro rats which are genetically deficient in AVP. Our results indicate that cardiac ANF mRNA and ANF content are higher in Brattleboro rats compared to Long-Evans controls, whereas the plasma levels are similar in both groups. Typical secretory granules containing immunoreactive ANF are present in ventricular cardiocytes of Brattleboro but not of Long-Evans rats. These data suggest that ANF release may be uncoupled from its synthesis in the absence of AVP.

Primary thrombocythemia in pregnancy: a report of two cases

We report two cases of primary thrombocythemia diagnosed during pregnancy. One patient developed transient visual field defects. She was treated with plateletpheresis at term and delivered of a normal child by cesarean section. The second patient was not treated. Intrauterine fetal death occurred at 36 weeks' gestation from multiple placental infarcts. In cases of primary thrombocythemia, we suggest close monitoring of both mother and fetus throughout pregnancy.

Quantitation of cell membrane glycoproteins in pathological conditions using a lectin-bound enzyme-linked immunosorbent assay (ELISA). Application to human platelets in the Bernard-Soulier syndrome

Several techniques are available to study cell membrane glycoproteins in pathological conditions but these either lack sensitivity or require radiolabelled material or expensive apparatus. We have, therefore, developed a sandwich-type enzyme-linked immunosorbent assay (ELISA) to study patients with the Bernard-Soulier syndrome (BSS), a hereditary platelet disorder characterized primarily, at the molecular level, by glycoprotein Ib (GpIb) deficiency. We have used the lectin wheat germ agglutinin to capture GpIb in the microtiter wells. Following incubation with monoclonal antibody AN51 which recognizes an epitope on GpIb, the immune complex was detected using the streptavidin-peroxidase-biotin complex. Platelet samples from 24 normal controls gave a mean value of 106% whereas in the six BSS patients the mean value was 14% and in the eight obligatory heterozygotes it was 78%. The technique is simple, inexpensive and sensitive and does not require the use of radioactive material. The assay method could be applied to quantitate other cellular glycoproteins where specific lectins and monoclonal antibodies are available.

Pro-opiomelanocortin gene: a model for negative regulation of transcription by glucocorticoids

The gene encoding pro-opiomelanocortin (POMC) offers an interesting model system to study negative control of transcription in eucaryotes. Indeed, glucocorticoid hormones specifically inhibit transcription of the POMC gene in the anterior pituitary. The POMC gene is predominantly expressed in the anterior and intermediate lobes of the pituitary. However, only anterior pituitary POMC transcription is inhibited by glucocorticoids and stimulated by corticotropin-releasing hormone (CRH). Rat POMC promoter sequences required for anterior pituitary-specific expression were localized between positions -480 and -34 base pairs (bp) by DNA-mediated gene transfer into the POMC-expressing tumor cells. AtT-20. These POMC promoter sequences also confer glucocorticoid inhibition of transcription. While two of the six in vitro binding sites for purified glucocorticoid receptor identified in the rat POMC gene are within these sequences, only one is required for glucocorticoid inhibition; this binding site is located at position -63 bp in the promoter and overlaps a putative CCAAT box sequence. The DNA sequence of the POMC -63 bp receptor binding site is homologous to receptor binding sites identified in the glucocorticoid responsive element (GRE) of glucocorticoid-inducible genes. However, DNA sequence divergencies between these sites, in particular within the conserved hexanucleotide sequence 5'-TGTYCT-3', may be involved in their opposite transcriptional activity. Alternatively, binding of the receptor in the promoter proximal region of the POMC gene may inhibit transcription by a hormone-dependent repressor mechanism.

Combined intraommaya methotrexate, cytosine arabinoside, hydrocortisone and thio-TEPA for meningeal involvement by malignancies

Twenty-three adult patients with meningeal involvement by a variety of malignancies were treated with the intra-Ommaya combination of methotrexate, hydrocortisone, cytosine arabinoside, and thio-TEPA. Whole brain irradiation was also administered to most patients who had not previously received it. Most patients demonstrated improvement of cerebrospinal fluid parameters, but only 50% of the patients experienced neurological improvement. Patients who did not receive cranial irradiation and performance status 4 patients were less likely to respond than were patients who did receive cranial irradiation as part of their treatment and patients who were performance status 0-3. Four patients developed possible and 2 patients developed probable or definite serious neurological complications. Another 4 patients developed less severe, reversible neurological toxicity. It is possible (but still uncertain) that this regimen is more toxic than other less intensive regimens, and further studies should be undertaken cautiously.

Tissue-specific activity of the pro-opiomelanocortin gene promoter

The pro-opiomelanocortin (POMC) gene is specifically expressed in corticotroph cells of the anterior pituitary. To define the POMC promoter sequences responsible for tissue-specific expression, we assessed POMC promoter activity by gene transfer into POMC-expressing pituitary tumor cells (AtT-20) and fibroblast L cells. The rat POMC promoter was only efficiently utilized and correctly transcribed in AtT-20 cells. 5'-End deletion analysis revealed two promoter regions required for activity in AtT-20 cells. When tested by fusion to a heterologous promoter, DNA fragments corresponding to both regions exhibited tissue-specific activity, suggesting the presence of at least two tissue-specific DNA sequence elements within the promoter. In summary, POMC promoter sequences from -480 to -34 base pairs appear sufficient to mimic the specificity of anterior pituitary expression.

Unusual proopiomelanocortin ribonucleic acids in extrapituitary tissues: intronless transcripts in testes and long poly(A) tails in hypothalamus

The POMC gene is predominantly expressed in the pituitary gland; it is also expressed in various extrapituitary tissues. While POMC mRNAs of similar size (approximately equal to 1000 nucleotides) are present in the anterior and neurointermediate lobes of the pituitary, other POMC-expressing tissues contain POMC mRNAs of different sizes. Longer POMC mRNAs are observed in the hypothalamus. Using S1 nuclease mapping and mRNA deadenylation by RNase H, we have shown that these large hypothalamic POMC mRNAs have longer poly(A) tails than pituitary POMC transcripts but contain the same transcripted sequences. In contrast, the testes contain POMC transcripts which are smaller than pituitary POMC mRNA. RNase and S1 nuclease mapping analyses suggest that these short transcripts do not contain sequences transcribed from pituitary exons 1 and 2. Indeed, as revealed by primer-extension experiments, these transcripts appear to initiate within exon 3 sequences of the POMC gene. The heterogeneous 5'-ends of these short testicular transcripts map into the NH2-terminal portion of the precursor in the region encoding gamma MSH; if ever translated, these transcripts would produce a form of POMC that would be truncated at the NH2-terminus and therefore would be devoid of any signal peptide sequence. Interestingly, the sequence of the short testicular transcripts corresponds to that of the mouse POMC pseudogene, suggesting that this POMC pseudogene may have derived from genomic integration of testicular transcripts via a cDNA intermediate.