The regulation of oxytocin receptor gene expression during adipogenesis.

Although it has been reported that oxytocin stimulates lipolysis in adipocytes, changes in the expression of oxytocin receptor (OTR) mRNA in adipogenesis are still unknown. The present study aimed to investigate the expression of OTR mRNA during adipocyte differentiation and fat accumulation in adipocytes. OTR mRNA was highly expressed in adipocytes prepared from mouse adipose tissues compared to stromal-vascular cells. OTR mRNA expression was increased during the adipocyte differentiation of 3T3-L1 cells. OTR expression levels were higher in subcutaneous and epididymal adipose tissues of 14-week-old male mice compared to 7-week-old male mice. Levels of OTR mRNA expression were higher in adipose tissues at four different sites of mice fed a high-fat diet than in those of mice fed a normal diet. The OTR expression level was also increased by refeeding for 4 h after fasting for 16 h. Oxytocin significantly induced lipolysis in 3T3-L1 adipocytes. In conclusion, a new regulatory mechanism is demonstrated for oxytocin to control the differentiation and fat accumulation in adipocytes via activation of OTR as a part of the hypothalamic-pituitary-adipose axis.

Involvement of prolactin-releasing peptide in the activation of oxytocin neurones in response to food intake.

Food intake activates neurones expressing prolactin-releasing peptide (PrRP) in the medulla oblongata and oxytocin neurones in the hypothalamus. Both PrRP and oxytocin have been shown to have an anorexic action. In the present study, we investigated whether the activation of oxytocin neurones following food intake is mediated by PrRP. We first examined the expression of PrRP receptors (also known as GPR10) in rats. Immunoreactivity of PrRP receptors was observed in oxytocin neurones and in vasopressin neurones in the paraventricular and supraoptic nuclei of the hypothalamus and in the bed nucleus of the stria terminalis. Application of PrRP to isolated supraoptic nuclei facilitated the release of oxytocin and vasopressin. In mice, re-feeding increased the expression of Fos protein in oxytocin neurones of the hypothalamus and bed nucleus of the stria terminalis. The increased expression of Fos protein in oxytocin neurones following re-feeding or i.p. administration of cholecystokinin octapeptide (CCK), a peripheral satiety factor, was impaired in PrRP-deficient mice. CCK-induced oxytocin increase in plasma was also impaired in PrRP-deficient mice. Furthermore, oxytocin receptor-deficient mice showed an increased meal size, as reported in PrRP-deficient mice and in CCKA receptor-deficient mice. These findings suggest that PrRP mediates, at least in part, the activation of oxytocin neurones in response to food intake, and that the CCK-PrRP-oxytocin pathway plays an important role in the control of the termination of each meal.

Mice heterozygous for the oxytocin receptor gene (Oxtr(+/-)) show impaired social behaviour but not increased aggression or cognitive inflexibility: evidence of a selective haploinsufficiency gene effect.

We characterised the behavioural phenotype of mice heterozygous (Oxtr(+/-)) for the oxytocin receptor gene (Oxtr) and compared it with that of Oxtr null mice (Oxtr(-/-)), which display autistic-like behaviours, including impaired sociability and preference for social novelty, impaired cognitive flexibility, and increased aggression. Similar to Oxtr(-/-) mice, the Oxtr(+/-) showed impaired sociability and preference for social novelty but, unlike the null genotype, their cognitive flexibility and aggression were normal. By autoradiography, Oxtr(+/-) mice were found to have approximately 50% fewer oxytocin receptors (OXTRs) in all of the examined brain regions. Thus, because a partial reduction in Oxtr gene expression is sufficient to compromise social behaviour, the Oxtr acts as a haploinsufficient gene. Furthermore, the inactivation of the Oxtr gene affects specific behaviours in a dose-dependent manner: social behaviour is sensitive to even a partial reduction in Oxtr gene expression, whereas defects in aggression and cognitive flexibility require the complete inactivation of the Oxtr gene to emerge. We then investigated the rescue of the Oxtr(+/-) social deficits by oxytocin (OT) and Thr(4)Gly(7)OT (TGOT) administered i.c.v. at different doses. TGOT was more potent than OT in rescuing sociability and social novelty in both genotypes. Furthermore, the TGOT doses that reverted impaired sociability and preference for social novelty in Oxtr(+/-) were lower than those required in Oxtr(-/-), thus suggesting that the rescue effect is mediated by OXTR in Oxtr(+/-) and by other receptors (presumably vasopressin V1a receptors) in Oxtr(-/-). In line with this, a low dose of the selective oxytocin antagonist desGlyDTyrOVT blocks the rescue effect of TGOT only in the Oxtr(+/-) genotype, whereas the less selective antagonist SR49059 blocks rescue in both genotypes. In conclusion, the Oxtr(+/-) mouse is a unique animal model for investigating how partial loss of the Oxtr gene impair social interactions, and for designing pharmacological rescue strategies.

Correlation between variable-number tandem-repeat-based genotypes and drug susceptibility in Mycobacterium avium isolates.

Little is known about the correlation between genotype and drug susceptibility in Mycobacterium avium (Mav) strains isolated from patients with Mav infections. To examine whether drug susceptibility profile of Mav is associated with genotype, we carried out variable-number tandem-repeat (VNTR) typing and drug susceptibility testing for Mav isolates from Japanese with nodular-bronchiectasis (NB)-type and cavitary disease (CA)-type diseases. We performed M. avium tandem repeat (MATR)-VNTR typing and drug susceptibility testing by the broth dilution method, using macrolides, rifamycins, ethambutol, isoniazid, aminoglycosides, and quinolones, for Mav isolates from patients with NB and CA-type diseases (NB-Mav and CA-Mav). Based on the VNTR genotyping, the Mav strains were grouped into three clusters. There was no difference with respect to the distribution of NB-Mav and CA-Mav among the clusters. We observed a strong association between VNTR genotype and susceptibility to quinolones (levofloxacin, moxifloxacin, gatifloxacin, sitafloxacin, and garenoxacin) and ethambutol. There was essentially no significant difference in drug susceptibility between NB- and CA-Mav strains, although NB-Mav was somewhat more resistant to fluoroquinolones, especially gatifloxacin, than CA-Mav. There was a significant association between VNTR genotype and susceptibility to quinolones and ethambutol in Mav isolates from Japanese patients.

Conditional knockout of Lgr4 leads to impaired ductal elongation and branching morphogenesis in mouse mammary glands.

We have analyzed the function of LGR4 in the development of various mouse epithelial tissues. Here we first report the retarded invasion of mammary ducts into the fat pad observed in Lgr4(K5 KO) mice at 4 weeks, compared with that of age-matched Lgr4(K5 ctrl). Furthermore, we demonstrate a significant decrease in mammary ductal branching in Lgr4(K5 KO) at several stages (4, 6 and 8 weeks). On the other hand, immunohistochemical analysis of the mammary gland of Lgr4(K5 KO) using anti-αSMA, anti-K18 and anti-laminin antibodies showed structures similar to those of Lgr4(K5 ctrl) mammary glands. In addition, we did not detect significant differences in the expression of ERα, which was suggested to be a downstream molecule of LGR4, and Lgr4(K5 KO) showed no retarded invasion in the response to 17ß-estradiol administration. Furthermore, the phosphorylated form of Smad1/5/8 was normally detected in the mammary gland of Lgr4(K5 KO).

Performance and quality analysis of membrane cartridges used in long-term operation.

In this study, operation and maintenance performance in two long-term operating Membrane Bioreactor (MBR) wastewater treatment facilities were investigated. One facility in Japan started its operation in 1999 showed that both effluent BOD and n-hexane extracts were less than 5 mg/L, and a cumulative replacement percentage (CR%) of membrane cartridges was 7.8% as of 2008. Another facility in the United Kingdom (UK) started its operation in 1998 showed that average effluent BOD was less than 5 mg/L and more than 5-log removal of faecal coliforms was maintained. The CR% was 6.4% as of 2008. Amongst 95 facilities in Europe, the CR% was 6.4% after 5-year operation. In order to inspect product quality of membrane cartridges after 10-year operation in the UK facility, clean water flow (CWF) rate and pore size distribution were measured. The CWF rate was approximately 100% of that of new membrane cartridge's, and the pore size distribution was well maintained at less than 0.46 microm. A microscopic observation showed some scratches on the membrane surface. However, they did not lead to deteriorate permeate quality. These data suggested that the membrane cartridges can be used as long as 10 years.

Interspecies somatic cell nucleus transfer with porcine oocytes as recipients: A novel bioassay system for assessing the competence of canine somatic cells to develop into embryos.

Interspecies somatic cell nucleus transfer (iSCNT) could be a useful bioassay system for assessing the ability of mammalian somatic cells to develop into embryos. To examine this possibility, we performed canine iSCNT using porcine oocytes, allowed to mature in vitro, as recipients. Canine fibroblasts from the tail tips and dewclaws of a female poodle (Fp) and a male poodle (Mp) were used as donors. We demonstrated that the use of porcine oocytes induced blastocyst formation in the iSCNT embryos cultured in porcine zygote medium-3. In Fp and Mp, the rate of blastocyst formation from cleaved embryos (Fp: 6.3% vs. 22.4%; and Mp: 26.1% vs. 52.4%) and the number of cells at the blastocyst stage (Fp: 30.7 vs. 60.0; and Mp: 27.2 vs. 40.1) were higher in the embryos derived from dewclaw cells than in those derived from tail-tip cells (P<0.05). The use of donor cells of any type in later passages decreased the rate of blastocyst formation. Treatment with trichostatin-A did not improve the rate of blastocyst formation from cleaved dewclaw cell-derived embryos but did so in the embryos derived from the tail-tip cells of Fp. Only blastocysts derived from dewclaw cells of Mp developed outgrowths. However, outgrowth formation was retrieved in the embryos derived from dewclaw cells of Fp by aggregation at the 4-cell stage. We inferred that iSCNT performed using porcine oocytes as recipients could represent a novel bioassay system for evaluating the developmental competence of canine somatic cells.

Association between mycobacterial genotypes and disease progression in Mycobacterium avium pulmonary infection.

BACKGROUND: Non-tuberculous mycobacterial lung disease, most commonly caused by Mycobacterium avium infection, tends to show variable disease progression, and significant disease predictors have not been adequately established. METHODS: Variable numbers of tandem repeats (VNTR) were evaluated in 16 mycobacterial interspersed repetitive unit (MIRU) loci from M avium isolates cultured from respiratory specimens obtained from 2005 to 2007. Specifically, the association between VNTR profiles and disease progression was assessed. RESULTS: Among the 37 subjects who provided positive respiratory cultures for M avium during the 2005-6 period, 15 subjects were treated within 10 months following a microbiological diagnosis of progressive M avium lung disease. Nine subjects underwent long-term follow-up (>24 months) without treatment for stable M avium lung disease. Based on a neighbour-joining cluster analysis used to classify M avium-positive subjects according to the VNTR profile, subjects with progressive versus stable lung disease were found to be grouped together in distinct clusters. Further analysis using logistic regression modelling showed that disease progression was significantly associated with the genetic distance of the M avium isolate from an appropriately selected reference (age-adjusted odds ratio 1.95; 95% confidence interval 1.16 to 3.30; p = 0.01 for the most significant model). A best-fit model could be used to predict the progression of M avium lung disease when subjects from the 2005-6 period were combined with those from 2007 (p = 0.003). CONCLUSION: Progressive lung disease due to M avium infection is associated with specific VNTR genotypes of M avium.

Bacteriological characteristics of Staphylococcus aureus isolates from humans and bulk milk.

The aim of this study was to clarify the epidemiological association and bacteriological characteristics of human and animal Staphylococcus aureus isolates. Pulsed-field gel electrophoresis showed that pulsotypes (PT) of isolates from bulk milk differed from PT from human isolates, suggesting that there is no epidemiological association between isolates from these 2 sources. The absence of a common PT could result from the lack of contact between the sources. Methicillin-resistant S. aureus from human secretions and S. aureus from bulk milk in Japan consisted of 1 and 2 dominant clusters, respectively, whereas methicillin-susceptible S. aureus from humans consisted of assorted clusters. Isolates belonging to the dominant clusters showed the coagulase serotype, the capsule serotype, detection of exotoxin genes, and antimicrobial susceptibility. Isolates from bulk milk did not show the penicillin-binding protein 2a gene, and 252 of 275 isolates belonging to the 2 dominant clusters of bulk milk were susceptible to ampicillin, cefazolin, erythromycin, chloramphenicol, oxacillin, and vancomycin. Moreover, the LukM/LukF'-PV leukotoxin gene was detected in 233 of 275 isolates belonging to the dominant clusters in bulk milk isolates. These results support the hypothesis that a number of factors play a role in the adaptation of S. aureus isolates to specific hosts.

Male-specific function of Dmrt7 by sexually dimorphic translation in mouse testis.

Dmrt7 is known to be an essential gene for spermatogenesis but not for oogenesis despite mRNA expression in both testis and ovary. In this study, we examined further expression of Dmrt7 transcript and protein. Northern blot and RT-PCR analysis revealed that there was an alternative splicing variant possessing the entire sequence of intron 1 in adult testis (intron 1 variant), in addition to the mature form of mRNA. In fetal ovary, the intron 1 variant was not expressed whereas the fully spliced form of mRNA was expressed. Immunohistochemical analyses demonstrated that DMRT7 protein was present only in spermatocytes of adult testis but not in fetal ovary. In situ hybridization analyses revealed that the fully spliced form of Dmrt7 mRNA as well as the intron 1 variant were expressed in spermatogonia, spermatids and Sertoli cells in addition to spermatocytes. We also found that poly(A) tails of Dmrt7 mRNA underwent modification of its length from 70 to 440 bp long. Unlike Arbp mRNA, the size variation of poly(A) tails was observed in immature testis in which spermatids were absent. In this study, we demonstrated that Dmrt7 had unique sexually dimorphic expression patterns in transcripts that associated with spermatocyte-specific translation, but not in ovary.

Molecular regulation of the oxytocin receptor in peripheral organs.

The oxytocin receptor belongs to the G-protein-coupled seven transmembrane receptor superfamily. Its main physiological role is regulating the contraction of uterine smooth muscle at parturition and the ejection of milk from the lactating breast. Oxytocin receptor expression is observed not only in the myometrium and mammary gland but also in the endometrium, decidua, ovary, testis, epididymis, vas deferens, thymus, heart and kidney, as well as in the brain. The expression profile shows a tissue-specific as well as a stage-specific pattern. The oxytocin receptor gene is a single-copy gene consisting of four exons and three introns, localized at 3p25-3p26.2 in the human chromosome. In transfection studies using a fusion construct containing the promoter region of the oxytocin receptor gene inserted in a reporter plasmid, neither proinflammatory cytokines nor oestrogen directly activate the gene. The nuclear fractions from up-regulated (term myometrium) and down-regulated (non-pregnant myometrium) tIssues show differential patterns of protein binding to the 5'-flanking region, and a human homologue of chicken MafF has been cloned as a term-myometrium-specific oxytocin receptor modulator. The oxytocin receptor gene appears to be highly methylated. Methylation around intron 1 and in intron 3 might contribute to tIssue-specific suppression of the gene. The oxytocin receptor is also regulated by desensitization, whose mechanism appears to involve loss of ligand-binding activity of the protein as well as suppression of the oxytocin receptor mRNA transcription. These findings taken together indicate that the oxytocin receptor is regulated in a very complicated manner, and the transcriptional regulatory elements critical for this regulation should be investigated further.

Successful pregnancy in a patient having high basal serum levels of sex steroid hormones.

A 25-year-old infertile woman who had higher basal levels of serum progesterone (P) and estradiol (E(2)) was examined. Ultrasonography and gonadotropin-releasing hormone test suggested polycystic ovarian syndrome. The high serum E(2) and P concentration increased even more along follicle growth and after ovulation, respectively. Although the source of the higher levels of steroids was unclear, she became pregnant with artificial insemination of husband's sperm and luteal support with human chorionic gonadotropin administration, and delivered a healthy newborn. Through the present study, we can conclude that the high basal level of P in follicular phase may not always impair reproduction, although several reports stress that it adversely affects oocyte maturation and fertilization, and is harmful to endometrial receptivity.

kdsA mutations affect FtsZ-ring formation in Escherichia coli K-12.

No one has, as yet, addressed the relationship between the nature of the outer membrane and cell division. kdsA encodes 3-deoxy-D-manno-octulosonic acid (KDO) 8-phosphate synthetase which catalyses the first step in the synthesis of KDO, the linker between lipid A and oligosaccharide of lipopolysaccharide (LPS). Seven temperature-sensitive mutants containing missense mutations in kdsA were affected in the production of KDO and all mutants stopped dividing at 41 degrees C and formed filaments with either one or no FtsZ ring. All observed defects were reversed by the plasmid-borne wild-type kdsA gene. Western blotting analysis, however, demonstrated that the amount of FtsZ protein was not affected by the mutation. The mutants were more susceptible to various hydrophobic materials, such as novobiocin, eosin Y and SDS at 36 degrees C. Methylene blue, however, restored kdsA mutant growth. Plasmid-borne wild-type msbA, encoding a lipid A transporter in the ABC family, partially suppressed kdsA mutation. A mutation of lpxA, functioning at the first stage in lipid A biosynthesis, inhibited both cell division and growth, producing short filaments. These results indicate that the instability of the outer membrane, caused by the defect in KDO biosynthesis, affects FtsZ-ring formation.

Identification of two cDNAs for human actin-related proteins (Arps) that have remarkable similarity to conventional actin.

We identified two cDNAs coding for the novel human actin-related proteins (Arps) hArpM1 and hArpM2. Both of them show remarkable similarity to conventional actin, and the ATP-binding motif and nuclear-export signals of actin are highly conserved. Their mRNAs are expressed in all tested human tissues, but in smaller amounts than that of actin. These features suggest that hArpM1 and M2 are involved in cytoskeletal organization like other cytoplasmic Arp subfamilies.

Prognostic factors of patients with yolk sac tumors of the ovary.

OBJECTIVE: Our purpose was to evaluate the prognostic factors in yolk sac tumors of the ovary. STUDY DESIGN: We performed a retrospective review of 47 patients with yolk sac tumors of the ovary from 1979 to 1997. RESULTS: Twenty-two patients had pure yolk sac tumors and 25 had germ cell tumors with yolk sac tissue as a component of the disease. The 5-year survival rate in stages I, II, III, and IV was 95%, 75%, 30%, and 25%, respectively. Patients with stage I disease had a more favorable prognosis than those with stage III and IV disease (P <.001). All patients who did not respond to chemotherapy died of this disease within 36 months of the first treatment. Chemotherapy regimens that included cisplatin gave better results than those without cisplatin (P <.05). The difference in prognosis was significant in cases in which the size of residual tumor was <2 cm in diameter (P <.01) and in cases in which ascites was either absent or <100 mL in volume (P <.05). Coexistence of other components of ovarian germ cell tumors in histologic specimens, preoperative serum alpha-fetoprotein level, fertility-sparing surgery, dissection of intrapelvic nodes, and p53 status had no significant correlation with the prognosis in this study. CONCLUSIONS: Staging and tumor-reductive surgery strongly affected the prognosis of this disease. Tumor-reductive surgery is advisable when ascites is minimal. Cisplatin-based chemotherapy after surgery was superior to chemotherapy without cisplatin; however, p53 status seemed to have no impact on chemosensitivity in yolk sac tumors of the ovary.

Molecular typing and epidemiological study of Salmonella enterica serotype Typhimurium isolates from cattle by fluorescent amplified-fragment length polymorphism fingerprinting and pulsed-field gel electrophoresis.

One hundred twenty Salmonella enterica serotype Typhimurium strains, including 103 isolates from cattle gathered between 1977 and 1999 in the prefecture located on the northern-most island of Japan, were analyzed by using fluorescent amplified-fragment length polymorphism (FAFLP) and pulsed-field gel electrophoresis (PFGE) to examine the genotypic basis of the epidemic. Among these strains, there were 17 FAFLP profiles that formed four distinct clusters (A, B, C, and D). Isolates that belonged to cluster A have become increasingly common since 1992 with the increase of bovine salmonellosis caused by serotype Typhimurium. PFGE resolved 25 banding patterns that formed three distinct clusters (I, II, and III). All the isolates that belonged to FAFLP cluster A, in which all the strains of definitive phage type 104 examined were included, were grouped into PFGE cluster I. Taken together, these results indicate that clonal exchange of serotype Typhimurium has taken place since 1992, and they show a remarkable degree of homogeneity at a molecular level among contemporary isolates from cattle in this region. Moreover, we have sequenced two kinds of FAFLP markers, 142-bp and 132-bp fragments, which were identified as a polymorphic marker of strains that belonged to clusters A and C, respectively. The sequence of the 142-bp fragment shows homology with a segment of P22 phage, and that of the 132-bp fragment shows homology with a segment of traG, which is an F plasmid conjugation gene. FAFLP is apparently as well suited for epidemiological typing of serotype Typhimurium as is PFGE, and FAFLP can provide a source of molecular markers useful for studies of genetic variation in natural populations of serotype Typhimurium.

Tumor metastasis-associated human MTA1 gene: its deduced protein sequence, localization, and association with breast cancer cell proliferation using antisense phosphorothioate oligonucleotides.

Using differential cDNA library screening techniques based on metastatic and nonmetastatic rat mammary adenocarcinoma cell lines we previously cloned and sequenced the metastasis-associated gene mta1. Using homology to the rat MTA1 gene we cloned the human MTA1 gene and found it to be overexpressed in a variety of human cell lines. We found a close similarity between the human MTA1 and rat MTA1 genes, as shown by 88% and 96% identities of the nucleotide and predicted amino acid sequences, respectively. Both genes encode novel proteins that contain a proline-rich region (SH3 binding motif), a putative zinc finger motif, a leucine zipper motif, and five copies of the SPXX motif often found in gene regulatory proteins. Using Southern blot analysis, the MTA1 gene was found to be highly conserved among all species examined; and using Northern blot analysis, MTA1 transcripts were found in virtually all cell lines of human origin that were analyzed, including melanoma and breast, cervix and ovarian carcinoma cells and normal breast epithelial cells. However, the expression level of the MTA1 gene in a normal breast epithelial cell was approximately 50% of that found in rapidly growing breast adenocarcinoma cell lines and an atypical mammary cell line. Experimental inhibition of MTA1 protein expression using antisense phosphorothioate oligonucleotides resulted in growth inhibition of human MDA-MB-231 breast cancer cells with relatively high expression of the MTA1 gene. Furthermore, the MTA1 protein was localized in the nuclei of cells transfected using a mammalian expression vector containing the full-length MTA1 gene. The results suggest that the MTA1 protein may function in cellular signaling processes important in the progression and growth of cancer cells, possibly as a nuclear regulatory factor.

Rapid molecular typing of Listeria monocytogenes by pulsed-field gel electrophoresis.

Pulsed-field gel electrophoresis (PFGE) is a highly discriminating tool for molecular typing, but the conventional PFGE protocol is time consuming. This paper describes a rapid method of PFGE for Listeria monocytogenes that yields results within 2 days.

Activin betaC and betaE genes are not essential for mouse liver growth, differentiation, and regeneration.

The liver is an essential organ that produces several serum proteins, stores vital nutrients, and detoxifies many carcinogenic and xenobiotic compounds. Various growth factors positively regulate liver growth, but only a few negative regulators are known. Among the latter are the transforming growth factor beta (TGF-beta) superfamily members TGF-beta1 and activin A. To study the function of novel activin family members, we have cloned and generated mice deficient in the activin betaC and betaE genes. Expression analyses demonstrated that these novel genes are liver specific in adult mice. Here, we show by RNase protection that activin betaC transcripts are present in the liver beginning at embryonic day 11.5 (E11.5) whereas activin betaE expression is detected starting from E17.5. Gene targeting in embryonic stem cells was used to generate mice with null mutations in either the individual activin betaC and betaE genes or both genes. In contrast to the structurally related activin betaA and betaB subunits, which are necessary for embryonic development and pituitary follicle-stimulating hormone homeostasis, mice deficient in activin betaC and betaE were viable, survived to adulthood, and demonstrated no reproductive abnormalities. Although activin betaC and betaE mRNAs are abundantly expressed in the liver of wild-type mice, the single and double mutants did not show any defects in liver development and function. Furthermore, in the homozygous mutant mice, liver regeneration after >70% partial hepatectomy was comparable to that in wild-type mice. Our results suggest that activin betaC and betaE are not essential for either embryonic development or liver function.

Homozygosity mapping of the locus responsible for renal tubular dysplasia of cattle on bovine chromosome 1.

Renal tubular dysplasia is a hereditary disease of Japanese black cattle showing renal failure and growth retardation with an autosomal recessive trait. In the present study, we mapped the locus responsible for the disease (RTD) by linkage analysis with an inbred paternal half-sib pedigree obtained from commercial herds. By analyzing segregation of microsatellite markers in the half-sibs, significant linkage was observed between the RTD locus and markers on bovine Chromosome (Chr) 1 with the highest lod score of 11.4. Homozygosity mapping with the inbred pedigree further defined the localization of the RTD locus in a 4-cM region between microsatellite markers BMS4003 and INRA119. Mapping of the RTD locus on bovine Chr 1 will facilitate cloning and characterization of the gene responsible for this disease.