Quality of life and clinical characteristics of self-improving congenital ichthyosis within the disease spectrum of autosomal-recessive congenital ichthyosis.

BACKGROUND: Autosomal-recessive congenital ichthyosis (ARCI) is a heterogeneous group of ichthyoses presenting at birth. Self-improving congenital ichthyosis (SICI) is a subtype of ARCI and is diagnosed when skin condition improves remarkably (within years) after birth. So far, there are sparse data on SICI and quality of life (QoL) in this ARCI subtype. This study aims to further delineate the clinical spectrum of SICI as a rather unique subtype of ARCI. OBJECTIVES: This prospective study included 78 patients (median age: 15 years) with ARCI who were subdivided in SICI (n = 18) and non-SICI patients (nSICI, n = 60) by their ARCI phenotype. METHODS: Quality of life (QoL) was assessed using the (Children's) Dermatology Life Quality Index. Statistical analysis was performed with chi-squared and t-Tests. RESULTS: The genetically confirmed SICI patients presented causative mutations in the following genes: ALOXE3 (8/16; 50.0%), ALOX12B (6/16; 37.5%), PNPLA1 (1/16; 6.3%) and CYP4F22 (1/16; 6.3%). Hypo-/anhidrosis and insufficient vitamin D levels (<30 ng/mL) were often seen in SICI patients. Brachydactyly (a shortening of the 4th and 5th fingers) was statistically more frequent in SICI (P = 0.023) than in nSICI patients. A kink of the ear's helix was seen in half of the SICI patients and tends to occur more frequently in patients with ALOX12B mutations (P = 0.005). QoL was less impaired in patients under the age of 16, regardless of ARCI type. CONCLUSIONS: SICI is an underestimated, milder clinical variant of ARCI including distinct features such as brachydactyly and kinking of the ears. Clinical experts should be aware of these features when seeing neonates with a collodion membrane. SICI patients should be regularly checked for clinical parameters such as hypo-/anhidrosis or vitamin D levels and monitored for changes in quality of life.

Specificity of RNA binding by CPEB: requirement for RNA recognition motifs and a novel zinc finger.

CPEB is an RNA binding protein that interacts with the maturation-type cytoplasmic polyadenylation element (CPE) (consensus UUUUUAU) to promote polyadenylation and translational activation of maternal mRNAs in Xenopus laevis. CPEB, which is conserved from mammals to invertebrates, is composed of three regions: an amino-terminal portion with no obvious functional motif, two RNA recognition motifs (RRMs), and a cysteine-histidine region that is reminiscent of a zinc finger. In this study, we investigated the physical properties of CPEB required for RNA binding. CPEB can interact with RNA as a monomer, and phosphorylation, which modifies the protein during oocyte maturation, has little effect on RNA binding. Deletion mutations of CPEB have been overexpressed in Escherichia coli and used in a series of RNA gel shift experiments. Although a full-length and a truncated CPEB that lacks 139 amino-terminal amino acids bind CPE-containing RNA avidly, proteins that have had either RRM deleted bind RNA much less efficiently. CPEB that has had the cysteine-histidine region deleted has no detectable capacity to bind RNA. Single alanine substitutions of specific cysteine or histidine residues within this region also abolish RNA binding, pointing to the importance of this highly conserved domain of the protein. Chelation of metal ions by 1,10-phenanthroline inhibits the ability of CPEB to bind RNA; however, RNA binding is restored if the reaction is supplemented with zinc. CPEB also binds other metals such as cobalt and cadmium, but these destroy RNA binding. These data indicate that the RRMs and a zinc finger region of CPEB are essential for RNA binding.

Identification and developmental expression of a smooth-muscle gamma-actin in postmeiotic male germ cells of mice.

Mouse testis contains two size classes of actin mRNAs of 2.1 and 1.5 kilobases (kb). The 2.1-kb actin mRNA codes for cytoplasmic beta- and gamma-actin and is found throughout spermatogenesis, while the 1.5-kb actin mRNA is first detected in postmeiotic cells. Here we identify the testicular postmeiotic actin encoded by the 1.5-kb mRNA as a smooth-muscle gamma-actin (SMGA) and present its cDNA sequence. The amino acid sequence deduced from the postmeiotic actin cDNA sequence was nearly identical to that of a chicken gizzard SMGA, with one amino acid replacement at amino acid 359, where glutamine was substituted for proline. The nucleotide sequence of the untranslated region of the SMGA differed substantially from those of other isotypes of mammalian actins. By using the 3' untranslated region of the testicular SMGA, a highly specific probe was obtained. The 1.5-kb mRNA was detected in RNA from mouse aorta, small intestine, and uterus, but not in RNA isolated from mouse brain, heart, and spleen. Testicular SMGA mRNA was first detected and increased substantially in amount during spermiogenesis in the germ cells, in contrast to the decrease of the cytoplasmic beta- and gamma-actin mRNAs towards the end of spermatogenesis. Testicular SMGA mRNA was present in the polysome fractions, indicating that it was translated. These studies demonstrate the existence of an SMGA in male haploid germ cells. The implications of the existence of an SMGA in male germ cells are discussed.

DNA methylation and demethylation events during meiotic prophase in the mouse testis.

The genes encoding three different mammalian testis-specific nuclear chromatin proteins, mouse transition protein 1, mouse protamine 1, and mouse protamine 2, all of which are expressed postmeiotically, are marked by methylation early during spermatogenesis in the mouse. Analysis of DNA from the testes of prepubertal mice and isolated testicular cells revealed that transition protein 1 became progressively less methylated during spermatogenesis, while the two protamines became progressively more methylated; in contrast, the methylation of beta-actin, a gene expressed throughout spermatogenesis, did not change. These findings provide evidence that both de novo methylation and demethylation events are occurring after the completion of DNA replication, during meiotic prophase in the mouse testis.

Weekly docetaxel and estramustine in patients with hormone-refractory prostate cancer.

The combination of docetaxel and estramustine has exhibited synergistic activity both in prostate cancer cell lines and in patients with hormone-refractory prostate cancer (HRPC). Based on these promising preclinical and phase I/II data, we conducted a study of weekly docetaxel and estramustine in patients with metastatic HRPC and a poor performance status. A total of 30 patients received (1) a 3-day course of oral estramustine during weeks 1 and 2 of each 3-week cycle plus (2) docetaxel, 35 mg/m(2) intravenously on day 2 of weeks 1 and 2. The median number of cycles per patient was 5, ranging from 1 to 22. The median patient age was 74 years (range, 61 to 90 years), and the median baseline Karnofsky performance status was 60% (range, 50% to 80%). Twenty-three patients (76%) had a > or =50% decrease in serum prostate-specific antigen (PSA); 17 (56%) of these patients had a > or =75% decrease in PSA. Pain scores and performance status likewise improved in 70% of patients. Three complete responses and four partial responses were observed among 12 patients with measurable disease. Toxicities were primarily nonhematologic in nature, with the most common being grade 1 through 3 nausea, asthenia, diarrhea, and edema. Given the activity and tolerability of weekly docetaxel and estramustine in this study, this regimen appears to be more suitable than previously studied docetaxel/estramustine administration schedules for treating metastatic HRPC in elderly patients with a poor performance status.

The effects of acute and chronic stresses on vasotocin gene transcripts in the brain of the rainbow trout (Oncorhynchus mykiss).

Secretion of adrenocorticotropic hormone (ACTH) from the fish pituitary, which occurs in times of stress, is stimulated by several hypothalamic neuropeptides, one of which is arginine vasotocin (AVT). This study investigates whether gene expression for AVT is up-regulated during acute or chronic stress. Rainbow trout (Oncorhynchus mykiss) were subjected to one of two forms of acute stress-either 2 h confinement followed by 2 h recovery, or capture and transfer to low water for 2 min followed by 4 h recovery in their home tank before autopsy. In other experiments, these stresses were repeated daily for 5 or 6 days (chronic stress). Quantification of AVT transcript prevalence in the parvocellular and magnocellular neurones of the preoptic nucleus after in situ hybridization was used as a monitor of the AVT gene response to stress. The results showed that acute confinement, but apparently not brief low-water stress, significantly increased AVT transcript prevalence in a group of parvocellular perikarya. When applied repeatedly, both forms of stress caused habituation, such that the AVT hybridization signal remained at control or even lower levels despite elevated pro-opiomelanocortin transcripts in the corticotropes and raised plasma cortisol concentrations. The AVT hybridization signal in the magnocellular perikarya showed no significant response to either acute or chronic stress. The results support the idea that these parvocellular AVT neurones are involved in ACTH stimulation during acute stress, and that the system habituates to chronic stresses.

Differences in arginine vasotocin gene transcripts and cortisol secretion in trout with high or low endogenous melanin-concentrating hormone secretion.

Previous studies on trout suggest that melanin-concentrating hormone (MCH) acts at both hypothalamic and pituitary levels to restrain the release of adrenocorticotropic hormone and hence cortisol during stress. Using in situ hybridization, the present work examined whether high rates of MCH secretion were associated with changes in the synthesis of arginine vasotocin (AVT), one of the corticotropin secretogogues. It also examined whether high endogenous MCH secretion restrains cortisol secretion during intense as well as mild stress, and how exogenous MCH affects the rise in plasma cortisol following injection stress. Trout were reared in black- or white-coloured tanks for 1 year or more to achieve maximal differences in MCH secretion. Following a mild stress, cortisol secretion was greater in black-reared fish with low MCH secretion which is in line with previous findings but, following a more severe stress, plasma cortisol concentrations were similar in the two groups. Injection of MCH into black-adapted fish restrained the stress-induced rise in plasma cortisol concentration during the first hour but did not affect final cortisol values. In two separate experiments, AVT mRNA levels were significantly lower in the hypothalamus of black-reared fish. Possible explanations for this include a greater negative-feedback restraint by cortisol, which is likely to rise higher in black-adapted fish during the moderate, daily stresses of aquarium life; or the possibility that exposure to a white background may be psychologically stressful, stimulating AVT transcription. The possibility that MCH directly stimulates AVT transcription cannot be excluded but seems less likely. The results suggest that while MCH may restrain the release of hypothalamo-pituitary stress hormones under moderately stressful conditions, it does not restrain AVT synthesis.

Utilization of an alternative transcription initiation site of somatic cytochrome c in the mouse produces a testis-specific cytochrome c mRNA.

The differential regulation of somatic and testis-specific cytochromes c during spermatogenesis in the mouse is accompanied by changes in mRNA length (Hake, L. E., Alcivar, A. A., and Hecht, N. B. (1990) Development 110, 249-257). In spermatogenic stem cells through early meiotic cells, we detect four somatic cytochrome c (cyt cs) mRNAs of 1.3, 1.1, and 0.7-0.5 kilobases (kb), whereas in postmeiotic cells we detect a larger cyt cs mRNA of 1.7 kb. Oligonucleotide-directed RNase H cleavage of cyt cs mRNA revealed that the 1.7-kb mRNA contains over 1 kb of 5'-untranslated region which is not present in the four shorter cyt cs mRNAs. RNase protection assays indicate that this additional sequence arises from the utilization of an alternative transcription initiation site of the functional cyt cs gene which is 1085 base pairs upstream of the initiation site for the four shorter cyt cs mRNAs. To analyze the promoter for the 1.7-kb mRNA, a genomic clone containing the cyt cs gene and 5 kb of 5'-flanking DNA was isolated. Sequence comparison of the putative promoter region with promoters of other postmeiotically expressed genes reveals several conserved regions. Utilization of this alternative initiation site may be involved in the down-regulation of cytochrome cs during spermatogenesis.

CPEB is a specificity factor that mediates cytoplasmic polyadenylation during Xenopus oocyte maturation.

The translational activation of several maternal mRNAs during Xenopus oocyte maturation is stimulated by cytoplasmic poly(A) elongation, which requires the uridine-rich cytoplasmic polyadenylation element (CPE) and the hexanucleotide AAUAAA. Here, we have enriched a CPE-binding protein (CPEB) by single-step RNA affinity chromatography, have obtained a CPEB cDNA, and have assessed the role of CPEB in cytoplasmic polyadenylation. The 62 kDa CPEB contains two RNA recognition motifs, and within this region, it is 62% identical to orb, an oocyte-specific RNA-binding protein from Drosophila. CPEB mRNA and protein are abundant in oocytes and are not detected in embryos beyond the gastrula stage. During oocyte maturation, CPEB is phosphorylated at a time that corresponds with the induction of polyadenylation. Immunodepletion of CPEB from polyadenylation-proficient egg extracts renders them incapable of adenylating exogenous RNA. Partial restoration of polyadenylation in depleted extracts is achieved by the addition of CPEB, thus demonstrating that this protein is required for cytoplasmic polyadenylation.

CPEB controls the cytoplasmic polyadenylation of cyclin, Cdk2 and c-mos mRNAs and is necessary for oocyte maturation in Xenopus.

Cytoplasmic polyadenylation is a key mechanism controlling maternal mRNA translation in early development. In most cases, mRNAs that undergo poly(A) elongation are translationally activated; those that undergo poly(A) shortening are deactivated. Poly(A) elongation is regulated by two cis-acting sequences in the 3'-untranslated region (UTR) of responding mRNAs, the polyadenylation hexanucleotide AAUAAA and the U-rich cytoplasmic polyadenylation element (CPE). Previously, we cloned and characterized the Xenopus oocyte CPE binding protein (CPEB), showing that it was essential for the cytoplasmic polyadenylation of B4 RNA. Here, we show that CPEB also binds the CPEs of G10, c-mos, cdk2, cyclins A1, B1 and B2 mRNAs. We find that CPEB is necessary for polyadenylation of these RNAs in egg extracts, suggesting that this protein is required for polyadenylation of most RNAs during oocyte maturation. Our data demonstrate that the complex timing and extent of polyadenylation are partially controlled by CPEB binding to multiple target sites in the 3' UTRs of responsive mRNAs. Finally, injection of CPEB antibody into oocytes not only inhibits polyadenylation in vivo, but also blocks progesterone-induced maturation. This is due to inhibition of polyadenylation and translation of c-mos mRNA, suggesting that CPEB is critical for early development.

Cellular localization of the mRNAs of the somatic and testis-specific cytochromes c during spermatogenesis in the rat.

During mammalian spermatogenesis, two forms of cytochrome c, cytochromes cs and ct, are present in male germ cells. During meiosis, cytochrome ct begins to replace cytochrome cs. At least four size classes of cytochrome cs mRNA are expressed in all somatic cells and in early stages of male germ cells. In addition, a cytochrome cs transcript of 1.7 kB has been detected in rodent testes and is abundant in post meiotic male germ cells. Here we utilize "in situ" hybridization to define the cellular sites where the four ubiquitous cytochrome cs transcripts, the 1.7 kB cytochrome cs transcripts, and the testis-specific cytochrome ct transcripts are expressed in the rat. Low levels of cytochrome cs mRNAs are detected in Leydig cells, myoepithelial cells, Sertoli cells, all types of spermatogonia, and during meiotic prophase. The 1.7 kB cytochrome cs mRNA is first detected in late stages of meiotic prophase and reaches its highest levels in steps 1 to 9 spermatids. No cytochrome cs mRNAs are detected in spermatids between steps 10 to 19. Low levels of cytochrome ct mRNAs, initially detected in zygotene spermatocytes, reach maximal levels in round spermatids. For all three probes the majority of the silver grains are localized randomly throughout the cytoplasm, suggesting that neither the translating nor non-translating (the 1.7 kB mRNA) forms of cytochrome cs mRNA nor the cytochrome ct mRNAs are sequestered during spermatogenesis. The absence of cytochrome cs or ct mRNAs in steps 10-19 spermatids suggest that the cytochrome ct protein does not turn over rapidly in late stage male germ cells.

DNA polymerase-beta and poly(ADP)ribose polymerase mRNAs are differentially expressed during the development of male germinal cells.

We have examined the steady-state mRNA levels in spermatogenic cells of two nuclear enzymes that appear to be involved in DNA repair, DNA polymerase-beta (pol-beta) and poly(ADP)ribose polymerase (PADPRP). Two pol-beta mRNAs of 1.3 kb and 1.4 kb were detected in extracts from mouse testes. In leptotene/zygotene spermatocytes a low level of the 1.4-kb mRNA was observed. Both pol-beta mRNAs were found in meiotic pachytene spermatocytes, with the 1.3-kb form being more abundant. In contrast, the 1.4-kb form was more abundant in haploid round spermatids. Polysome gradient analyses indicated that the two pol-beta mRNAs were predominantly present in the nonpolysomal fractions of spermatocytes. In round spermatids, a larger fraction of the 1.4-kb pol-beta mRNA was associated with polysomes, correlating well with the higher levels of pol-beta enzyme detected during spermiogenesis. The pattern of PADPRP mRNA expression differed from the expression of pol-beta mRNA. The two PADPRP mRNAs of 3.7 and 3.8 kb were present in type A and type B spermatogonia, reached their highest levels in pachytene spermatocytes, and were greatly reduced in haploid round and elongating spermatids. Most of the pachytene spermatocyte PADPRP and mRNAs were present in polysomes, whereas a greater percentage of PADPRP mRNAs in round spermatids were detected in the nonpolysomal fractions. This finding correlates with the immunocytochemical nuclear localization of this enzyme in pachytene spermatocytes. These data demonstrate that different developmental patterns of mRNA expression and translational regulation exist for the pol-beta and PADPRP mRNAs during differentiation of male germinal cells.

CPEB degradation during Xenopus oocyte maturation requires a PEST domain and the 26S proteasome.

Cytoplasmic poly(A) elongation is widely utilized during the early development of many organisms as a mechanism for translational activation. Targeting of mRNAs for this mechanism requires the presence of a U-rich element, the cytoplasmic polyadenylation element (CPE), and its binding protein, CPEB. Blocking cytoplasmic polyadenylation by interfering with the CPE or CPEB prevents the translational activation of mRNAs that are crucial for oocyte maturation. The CPE sequence and CPEB are also important for translational repression of mRNAs stored in the Xenopus oocyte during oogenesis. To understand the contribution of protein metabolism to these two roles for CPEB, we have examined the mechanisms influencing the expression of CPEB during oogenesis and oocyte maturation. Through a comparison of CPEB mRNA levels, protein synthesis, and accumulation, we find that CPEB is synthesized during oogenesis and stockpiled in the oocyte. Minimal synthesis of CPEB, <3.6%, occurs during oocyte maturation. In late oocyte maturation, 75% of CPEB is degraded coincident with germinal vesicle breakdown. Using proteasome and ubiquitination inhibitors, we demonstrate that CPEB degradation occurs via the proteasome pathway, most likely through ubiquitin-conjugated intermediates. In addition, we demonstrate that degradation requires a 14 amino acid PEST domain.

Changes in mRNA length accompany translational regulation of the somatic and testis-specific cytochrome c genes during spermatogenesis in the mouse.

The mouse testis contains two isotypes of cytochrome c, which differ in 14 of 104 amino acids: cytochrome cs is present in all somatic tissues and cytochrome cT is testis specific. The regulation of cytochrome cS and cytochrome cT gene expression during spermatogenesis was examined by Northern blot analysis using specific cDNA probes. Total RNA was isolated from adult tissues, enriched germinal cell populations and polysomal gradients of total testis and isolated germinal cells. Three cytochrome cS mRNAs were detected averaging 1.3 kb, 1.1 kb and 0.7 kb in all tissues examined; an additional 1.7 kb mRNA was observed in testis. Isolated germinal cells through prepuberal pachytene spermatocytes contained only the three smaller mRNAs; the 1.7 kb mRNA was enriched in round spermatids. All three smaller cytochrome cS mRNAs were present on polysomes; the 1.7 kb mRNA was non-polysomal. Cytochrome cT mRNA of 0.6-0.9 kb was detected in testis; mRNA levels were low in early spermatogonia and peaked in prepuberal pachytene spermatocytes. In adult pachytene spermatocytes, a subset of the cytochrome cT mRNAs, 0.7-0.9 kb, was present on polysomes; a shortened size class, 0.6-0.75 kb, was non-polysomal. A distinct, primarily non-polysomal, cytochrome cT 0.7 kb mRNA was present in round spermatids. These results indicate that (1) both cytochrome cS and cytochrome cT mRNAs are present in early meiotic cells, (2) a 1.7 kb cytochrome cS mRNA is post-meiotically expressed and non-polysomal and (3) cytochrome cS and cytochrome cT mRNAs are each developmentally and translationally regulated during spermatogenesis.

Phenogenetics of triploid intersexes in Drosophila melanogaster.

Triploid intersexes homozygous for a mutant (msl-2) known to impede the hyperactivation of the X chromosome in diploid males differentiate into adults, sexually indistinguishable from their heterozygous sibs. A shift toward female sexual differentiation mediated by manipulating the rearing temperature is accompanied by an apparent increase in the level of an X-linked gene product. This unexpected result is rationalized in terms of differential lethality of individuals at the two extremities of the distribution of X-activity levels in intersexes raised at a particular temperature. No evidence of a mosaicism comparable to the sexual mosaicism exhibited could be found with respect to an X-linked gene product in triploid intersexes.

The genes encoding the somatic and testis-specific isotypes of the mouse cytochrome c genes map to paralogous regions of chromosomes 6 and 2.

Using mouse probes specific to cytochrome cs and to cytochrome cT, the single-copy genes encoding these two proteins have been mapped to paralogous chromosomal regions by analysis of restriction fragment length variants in interspecific crosses. The gene for cytochrome cs, Cycs, maps to a position between Tcrb and Cbl-1 on proximal mouse Chromosome 6, and the gene for cytochrome cT, Cyct, maps between Gad-1 and Sfpi-1 on mouse Chromosome 2.

junD mRNA expression differs from c-jun and junB mRNA expression during male germinal cell differentiation.

The members of the jun family of protooncogenes (junB, c-jun, and junD) share a high degree of sequence homology and function as transcriptional regulators. Here we compare the pattern of junD mRNA expression during spermatogenesis to that of junB and c-jun (Alcivar et al.: J Biol Chem 265:20160-20165, 1990). junD transcripts are present at high levels in total RNA obtained from both prepuberal and adult intact testes, with the highest levels at stages containing predominantly premeiotic and postmeiotic germ cells. Analyses of cells isolated from testes of 8-day-old mice indicate that the level of the 1.8 kb junD mRNA is higher in type B spermatogonia than in type A spermatogonia. In testes of 17-day-old mice, the highest junD mRNA levels are detected in preleptotene spermatocytes compared to leptotene/zygotene and prepuberal pachytene spermatocytes. In cells from adult testes, the junD mRNA levels are higher in postmeiotic round spermatids and residual bodies/cytoplasts than in meiotic pachytene spermatocytes. An additional junD transcript of about 1.6 kb is detected in postmeiotic cells. Analyses of polysomal and nonpolysomal RNAs prepared from isolated testicular cells indicate that in early meiotic cell types the junD transcript is more efficiently loaded onto polysomes than in later cell types. In summary, the pattern of expression of junD differs from that of junB and c-jun during spermatogenesis most notably in that 1) junD mRNA levels do not increase following dissociation of testicular cells and 2) in contrast to the nearly undetectable levels of junB and c-jun mRNAs in adult postmeiotic testicular cells, high levels of junD mRNAs are seen.(ABSTRACT TRUNCATED AT 250 WORDS)

DNA methyltransferase is developmentally expressed in replicating and non-replicating male germ cells.

Genomic methylation patterns are established during maturation of primordial germ cells and during gametogenesis. While methylation is linked to DNA replication in somatic cells, active de novo methylation and demethylation occur in post-replicative spermatocytes during meiotic prophase (1). We have examined differentiating male germ cells for alternative forms of DNA (cytosine-5)-methyltransferase (DNA MTase) and have found a 6.2 kb DNA MTase mRNA that is present in appreciable quantities only in testis; in post-replicative pachytene spermatocytes it is the predominant form of DNA MTase mRNA. The 5.2 kb DNA MTase mRNA, characteristic of all somatic cells, was detected in isolated type A and B spermatogonia and haploid round spermatids. Immunobolt analysis detected a protein in spermatogenic cells with a relative mass of 180,000-200,000, which is close to the known size of the somatic form of mammalian DNA MTase. The demonstration of the differential developmental expression of DNA MTase in male germ cells argues for a role for testicular DNA methylation events, not only during replication in premeiotic cells, but also during meiotic prophase and postmeiotic development.

Translation of a unique transcript for protein isoaspartyl methyltransferase in haploid spermatids: implications for protein storage and repair.

The mammalian testis contains high levels of a protein, L-isoaspartyl (D-aspartyl) O-methyltransferase (PIMT), postulated to play a role in the repair of age-damaged proteins. To examine the regulation of PIMT concentrations during the development of spermatozoa, poly(A)+ RNA was isolated from purified populations of pachytene spermatocytes and round spermatids. Northern blot analysis revealed that a unique 1.1-1.3 kb PIMT transcript is present in preparations of round spermatid and pachytene spermatocyte poly (A)+ RNA. The concentration of this small PIMT transcript is at least four times higher in mRNA isolated from round spermatids than in mRNA isolated from pachytene spermatocytes, indicating that the PIMT gene is actively transcribed during the haploid phase of spermatogenesis. The germ cell-specific PIMT transcripts are distributed between the polysomal fraction and the nonpolysomal fractions of testis RNA, suggesting that translational controls also contribute to the high concentrations of PIMT in mammalian sperm. PIMT function is not essential for spermatogenesis because the testes from transgenic mice lacking PIMT activity have normal levels of protamine transcripts, and because functional sperm can be recovered from the cauda epididymis. The protein repair function of the PIMT may be more important in maintaining the fertilization competence of translationally-inactive mature sperm during the prolonged period of epididymal transit and storage in the male reproductive tract.