[Outcomes of the second pregnancy after Triple-P procedure in women complicated with placenta accreta spectrum disorders].

Objective: To investigate the safety of the Triple-P procedure in women complicated with severe placenta accreta spectrum disorders (PAS) and its influence on second pregnancy. Methods: From January 2015 to December 2017, the outcomes of the second pregnancy after the Triple-P procedure in 11 pregnant women complicated with PAS in the Third Affiliated Hospital of Guangzhou Medical University and the First Affiliated Hospital of Zhengzhou University were retrospectively analyzed. Results: By December 2021, a total of 11 pregnant women who underwent the Triple-P procedure for PAS had a second pregnancy, with a median interval of 3 years (2-3 years). Of the 11 pregnant women, 7 delivered after 36 weeks of gestation. The median gestational age was 38 weeks, and 4 terminated within the first trimester. PAS recurred in 1 of 7 pregnant women (1/7) and was associated with placenta previa. All of the 7 pregnant women were delivered by cesarean section, with a median postpartum blood loss of 300 ml (200-450 ml), and only one pregnant woman required blood transfusion. None of the pregnant women were transferred to the intensive care unit, and there were no uterine rupture, bladder injury, puerperal infection, and neonatal adverse outcomes. Conclusion: Pregnant women who underwent the Triple-P procedure for severe PAS could be considered for second pregnancy with strictly management by an experienced multidisciplinary team, which may result in a good outcome.

[Comparative study of unilateral biportal endoscopy and coaxial large channel endoscopy for lumbar spinal stenosis].

Objective: To compare the efficacy of unilateral biportal endoscopy (UBE) and coaxial large channel endoscopy for lumbar spinal stenosis. Methods: A total of 176 patients with lumbar spinal stenosis treated in Tianjin Hospital from March 2015 to October 2021 were included in this study. Of the patients, 110 cases were treated with UBE, including 52 males and 58 females, with a mean age of (75.1±10.4) years; while 66 cases were treated with coaxial large channel endoscopy, including 31 males and 35 females, with an average age of (77.2±13.1) years. The visual analogue scale (VAS) score of pain and Oswestry disability index (ODI) were compared before and after surgery between the two groups, with the improvement rate calculated. The operation time, intraoperative blood loss, perioperative conditions and complications were compared. The operation efficacy was evaluated according to MacNab scale and was compared between the two groups. Results: There was no significant differences in age, gender, disease course, VAS of pain, ODI and index levels between the two groups before operation (all P>0.05). The operation time and postoperative drainage in UBE group and coaxial large channel endoscopy group were comparable [(60.1±12.4)min, (62.5±13.2)min and (103.8±20.7)ml, (98.5±22.1)ml, respectively, both P>0.05]. After the operation, the VAS score of low back pain, VAS score of leg pain and ODI of the two groups were all lower than those before operation, and decreased continuously during follow-up; and under the repeated measures analysis of variance, significant differences were found between different time points (all P<0.05), no significant difference was found between the two groups (all P>0.05), nor interaction between groups and time points was detected (all P>0.05). The patients were followed-up for (18.0±4.2) months (6 to 30 months). There was no significant difference in VAS and ODI improvement rates and excellent rate of efficacy between the two groups at the last follow-up (all P>0.05). Conclusions: Both UBE and coaxial large channel endoscopy can provide excellent results for lumbar spinal stenosis. UBE has sufficient decompression and is convenient to explore and remove the herniated disc.

Characteristics of abnormal subjects in screening of tumor markers among middle-aged and elderly people in Weihai area.

OBJECTIVE: Based on the Huimin policy of Weihai Social Security Bureau, this project aims to investigate feasibility of screening through screening of serum tumor markers (TM) in the middle-aged and elderly population in Weihai area. According to the joint mode of examination institution and clinical department (oncology), we provide dynamic follow-up for subjects for early intervention of abnormal tumor screening and high-risk population, through which we can cut off pathogenic pathway of cancer and improve early diagnosis of cancer and enhance the cure rate. PATIENTS AND METHODS: We continued to track subjects whose TM was not reduced to normal until it was normal or diagnosed, collecting the blood samples of eligible patients that we removed high-risk factors from the subjects so that TM could be lowered to normal. RESULTS: A total of 83,049 blood samples were detected in our hospital, and 89 patients were diagnosed with newly diagnosed tumor. The positive expression rate of CEA in lung cancer patients was 91.4%. CONCLUSIONS: The diagnosis of tumor relies not only on TM, but also on observation of clinical symptoms, continuous observation of TM dynamic changes and individualized comprehensive analysis.  The main purpose of this policy is not only to find patients with "early tumor", but also to cut off the pathogenic pathway of cancer, achieve purpose of tertiary prevention and significantly save medical costs. The examination mechanism and the clinical-related departments are connected, and the pattern of screening, tracking and analysis of abnormal results in large samples is in line with the present situation of China and is worthy of clinical promotion.

[Forcasting the prevalence of myopia among students aged 6-18 years in China from 2021 to 2030].

Objective: To predict the prevalence of myopia among Chinese students aged 6-18 years under different intervention scenarios from 2021 to 2030. Methods: The multi-state Markov model was developed based on the transition process of study stages and myopia statuses. The development of myopia was simplified into two statuses: non-myopia and myopia. Students aged 6-18 years were also divided according to their study stages including senior kindergarten, primary school (from Grade 1 to 6), junior school (from Grade 1 to 3) and high school (from Grade 1 to 3). The parameters were extracted from the National Myopia Investigation in 2018 and published articles of cohort studies. The transition probability was applied to simulate the intervention scenarios, and sensitivity analysis was carried out. Results: The cumulative incidence of myopia among Chinese school-aged children and adolescents would increase consistently. It would be 91.3% (min to max: 83.7% to 96.7%) upon graduation from high school. Without any intervention, the myopia prevalence would increase to 61.8% (min to max: 55.4% to 69.5%) by 2030 among Chinese school-aged children and adolescents. And the myopia prevalence among students in primary schools, junior schools and high schools would be 45.6% (min to max: 40.2% to 54.3%), 81.3% (min to max: 72.6% to 91.0%) and 90.5% (min to max: 82.4% to 96.7%), respectively, all higher than the national target. If the interventions could achieve 70% of the desired effect, the myopia prevalence would be lower than the national target at each stage. Conclusions: Without effective interventions, the prevalence of myopia among students aged 6-18 years may keep increasing in the next ten years. If the interventions achieve the desired effect, the national target for myopia prevention and control could be reached. It is urgent to identify more effective interventions and call on the whole society to participate in the myopia prevention action to achieve the national goal by 2030. (Chin J Ophthalmol, 2021, 57: 261-267).

LncRNA MT1JP inhibits the malignant progression of hepatocellular carcinoma through regulating AKT.

OBJECTIVE: The purpose of this study was to investigate the expression profile of long non-coding RNA (lncRNA) MT1JP in hepatocellular carcinoma (HCC), and to explore the relationship between its expression level and the clinical indicators, as well as the prognosis of HCC patients. PATIENTS AND METHODS: In this study, the expression level of MT1JP in 45 pairs of tumor tissue specimens and paracancerous ones collected from HCC patients were examined through quantitative Real Time-Polymerase Chain Reaction (qRT-PCR) method, and the interplay between MT1JP expression and clinical indicators, as well as the prognosis of HCC patients, was also analyzed. Meanwhile, the expression of MT1JP in HCC cell lines was further verified by qRT-PCR. In addition, MT1JP overexpression model was constructed using lentivirus in HCC cell lines (Hub7 and HepG2), and then, Cell Counting Kit-8 (CCK-8), cell colony formation assay, and flow cytometry were performed to examine the impact of MT1JP on the HCC cell functions. Additionally, whether MT1JP exerts its biological characteristics through protein kinase B (AKT) was finally explored. RESULTS: In this experiment, qRT-PCR results showed that the expression level of lncRNA MT1JP in tumor tissues of HCC patients was remarkably lower than that in adjacent tissues, and the difference was statistically significant. Meanwhile, compared with patients with high expression of MT1JP, patients with low expression of MT1JP had a higher pathological staging and a lower overall survival rate. In addition, overexpression of MT1JP remarkably attenuated the proliferation ability of HCC cells but enhanced cell apoptosis rate at the same time. Finally, Western blot results revealed that the overexpression of MT1JP may markedly reduce the AKT expression, thereby suppressing the malignant progression of HCC. CONCLUSIONS: LncRNA MT1JP expression is remarkably decreased in HCC tumor tissue samples, which is associated with pathological stage and poor prognosis of HCC patients. In addition, MT1JP may inhibit the malignant progression of HCC by downregulating AKT.

Protective effect of resveratrol on kidney in rats with diabetic nephropathy and its effect on endoplasmic reticulum stress.

OBJECTIVE: Diabetic nephropathy (DN) can cause chronic renal insufficiency and significantly reduce the life quality of patients with diabetes mellitus, and may eventually lead to death. The study investigated the expression of endoplasmic reticulum stress-related factors, which have important roles in the progress of DN and to explore effects of resveratrol on DN and the possible mechanism. MATERIALS AND METHODS: Specific pathogen free (SPF) grade healthy male Sprague Dawley (SD) rats were divided into different groups for different treatments. The diabetic rat model was established by intraperitoneal injection of low-dose streptozotocin (STZ) (40 mg/kg). The normal rats and diabetes model rats were divided into four groups including normal control group (N), normal control + resveratrol (N+R), model group (M), and model + resveratrol group (M+R) for different treatments. The changes of renal histology were observed by immunohistochemistry. Glucose oxidase/peroxidase method was used to measure FPG, UP 24 h content was measured by bicinchoninic acid (BCA) assay, BUN, Scr and Cys C content were measured by automatic biochemical analyzer. The expressions of 78 kDa glucose-regulated protein (GRP78), protein kinase RNA-like endoplasmic reticulum kinase (PERK), and activating transcription factor 4 (ATF4) and C/EBP-homologous protein (CHOP) were analyzed by Western blot. RESULTS: Resveratrol treatment significantly reduced the fasting blood glucose level, urinary protein level and renal pathological damage. The phosphorylation of PERK in the kidney of rats with diabetes was up-regulated, while resveratrol treatment reduced this change. The expression of p- PERK, GRP78, ATF4, and CHOP was significantly increased in rats with diabetes, while resveratrol treatment can reduce the increased level of those endoplasmic reticulum stress related factors. CONCLUSIONS: Resveratrol has a good therapeutic effect on DN in rats without side effect. The mechanism may be related to the regulation of endoplasmic reticulum stress response.

[RET pro-oncogene and medullary thyroid carcinoma].

Medullary thyroid carcinoma (MTC) originats from the parafollicular C cells of the thyroid, which is one of the most aggressive forms of thyroid malignancy with the poor prognosis. Hereditary MTC has multiple endocrine neoplasia types 1, 2A and 2B. The mutation of RET proto-oncogene has been identified as the main cause of MTC, and all mutations locate among the exons 5, 8, 10, 11, 13, 14, 15, and 16. Mutation analysis of the RET may provide a theoretical basis for the prevention, diagnosis and treatment of MTC.

Molecular cloning and tissue distribution profiles of the chicken R-spondin1 gene.

Rspo1 belongs to the Rspo family, which is composed of 4 members (Rspo1-4) that share 40 to 60% sequence homology and similar domain organizations, and regulate the WNT signaling pathway via a common mechanism. Rspo1 plays a key role in vertebrate development and is an effective mitogenic factor of gastrointestinal epithelial cells. We report the cloning of chicken Rspo1 and its gene expression distribution among tissues. It contained an open reading frame of 783 bp encoding a protein of 260 amino acids, and its molecular weight was predicted to be 28.80 kDa. Reverse transcription-polymerase chain reaction-based gene expression analysis indicated that chicken Rspo1 was highly expressed in the stomach muscle tissue, but was expressed at low levels in the lung, brain, jejunum, cecum, ileum, spleen, pancreas, kidney, and glandular stomach. These results suggest that Rspo1 plays a major role in muscular immune protection.

Glycation exacerbates the neuronal toxicity of ß-amyloid.

Accumulation evidence shows that ß-amyloid (Aß) is a neurotoxic and accumulation of Aß is responsible for the pathology of Alzheimer's disease (AD). However, it is currently not fully understood what makes Aß toxic and accumulated. Previous studies demonstrate that Aß is a suitable substrate for glycation, producing one form of the advanced glycation endproducts (AGEs). We speculated that Aß-AGE formation may exacerbate the neurotoxicity. To explore whether the Aß-AGE is more toxic than the authentic Aß and to understand the molecular mechanisms, we synthesized glycated Aß by incubating Aß with methylglyoxal (MG) in vitro and identified the formation of glycated Aß by fluorescence spectrophotometer. Then, we treated the primary hippocampal neurons cultured 8 days in vitro with Aß-AGE or Aß for 24 h. We observed that glycation exacerbated neurotoxicity of Aß with upregulation of receptor for AGE (RAGE) and activation of glycogen synthase kinase-3 (GSK-3), whereas simultaneous application of RAGE antibody or GSK-3 inhibitor reversed the neuronal damages aggravated by glycated Aß. Thereafter, we found that Aß is also glycated with an age-dependent elevation of AGEs in Tg2576 mice, whereas inhibition of Aß-AGE formation by subcutaneously infusion of aminoguanidine for 3 months significantly rescued the early cognitive deficit in mice. Our data reveal for the first time that the glycated Aß is more toxic. We propose that the glycated Aß with the altered secondary structure may be a more suitable ligand than Aß for RAGE and subsequent activation of GSK-3 that can lead to cascade pathologies of AD, therefore glycated Aß may be a new therapeutic target for AD.

Audiological and genetic features of the mtDNA mutations.

CONCLUSIONS: Significant difference in the incidence of mitochondrial DNA (mtDNA) mutations was found between the Chinese and USA populations. The identification of the mtDNA A1555G mutation in a large proportion of Chinese probands with nonsyndromic sensorineural hearing loss (NSHL) provides a molecular explanation for the high prevalence of aminoglycoside-induced deafness in China. OBJECTIVE: The aim was to characterize the audiological and genetic features of NSHL due to mutations in mtDNA. SUBJECTS AND METHODS: The mtDNA and audiogram analyses were performed in 498 NSHL patients (290 from China and 208 from the USA) with and without history of aminoglycoside exposure. A PCR and restriction enzyme digestion protocol was used for mutational screening and the European Workshop on Genetic Hearing Loss criteria were applied for audiological classification. RESULTS: All Chinese probands (15.5%) with mtDNA mutation were found to carry the homoplasmic mtDNA A1555G mutation, whereas four probands (1.9%) from the USA were found to carry the mtDNA A1555G and two (1%) had mtDNA G7444A. Approximately 63% of the probands with mtDNA mutations had post-lingual hearing loss and 56.8% of them had a medical history of exposure to aminoglycosides. Hearing losses are bilateral, sensorineural, and symmetric. The main audiogram shapes found were sloping.

A novel DFNA5 mutation, IVS8+4 A>G, in the splice donor site of intron 8 causes late-onset non-syndromic hearing loss in a Chinese family.

We report here the clinical, genetic, and molecular characteristics of a large Chinese family exhibiting non-syndromic, late-onset autosomal dominant sensorineural hearing loss. Clinical evaluation revealed variable phenotypes of hearing loss in terms of severity and age-at-onset of disease in these subjects. Genome-wide linkage analysis mapped the disease gene to the DFNA5 locus with a maximum two-point log odds score of 5.39 at [theta] = 0 for marker D7S2457. DNA sequencing of DFNA5 revealed a novel heterozygous IVS8+4 A>G substitution in the splice donor site of intron 8. Reverse transcriptase-polymerase chain reaction (RT-PCR) showed skipping of exon 8 in the mutant transcript. This mutation faithfully cosegregated with hearing loss in the family. In addition, the mutation was absent in 100 unrelated control DNA samples of Chinese origin. The IVS8+4 A>G mutation is predicted to create a shift in the reading frame and introduce a stop codon at position 372, thereby resulting in a prematurely truncated DFNA5 protein. Up to date, a total of four mutations in DFNA5 have been reported to lead to hearing impairment, all of them result in skipping of exon 8 at the mRNA level. Our findings provide further support for the hypothesis that DFNA5-associated hearing loss is caused by a very specific gain-of-function mutation.

An isoform of GTPase regulator DOCK4 localizes to the stereocilia in the inner ear and binds to harmonin (USH1C).

The driving forces for the regulation of cell morphology are the Rho family GTPases that coordinate the assembly of the actin cytoskeleton. This dynamic feature is a result of tight coupling between the cytoskeleton and signal transduction and is facilitated by actin-binding proteins (ABPs). Mutations in the actin bundling and PDZ domain-containing protein harmonin are the causes of Usher syndrome type 1C (USH1C), a syndrome of congenital deafness and progressive blindness, as well as certain forms of non-syndromic deafness. Here, we have used the yeast two-hybrid assay to isolate molecular partners of harmonin and identified DOCK4, an unconventional guanine exchange factor for the Rho family of guanosine triphosphatases (Rho GEF GTPases), as a protein interacting with harmonin. Detailed molecular analysis revealed that a novel DOCK4 isoform (DOCK4-Ex49) is expressed in the brain, eye and inner ear tissues. We have further provided evidence that the DOCK4-Ex49 binds to nucleotide free Rac as effectively as DOCK2 and DOCK4 and it is a potent Rac activator. By immunostaining using a peptide antibody specific to DOCK4-Ex49, we showed its localization in the inner ear within the hair bundles along the stereocilia (SC). Together, our data indicate a possible Rac-DOCK4-ABP harmonin-activated signaling pathway in regulating actin cytoskeleton organization in stereocilia.

A novel locus for autosomal dominant non-syndromic deafness, DFNA53, maps to chromosome 14q11.2-q12.

BACKGROUND: Non-syndromic hearing loss is among the most genetically heterogeneous traits known in humans. To date, at least 50 loci for autosomal dominant non-syndromic sensorineural hearing loss (ADNSSHL) have been identified by linkage analysis. OBJECTIVE: To report the mapping of a novel autosomal dominant deafness locus on the long arm of chromosome 14 at 14q11.2-q12, DFNA53, in a large multigenerational Chinese family with post-lingual, high frequency hearing loss that progresses to involve all frequencies. RESULTS: A maximum multipoint LOD score of 5.4 was obtained for marker D14S1280. The analysis of recombinant haplotypes mapped DFNA53 to a 9.6 cM region interval between markers D14S581 and D14S1021. Four deafness loci (DFNA9, DFNA23, DFNB5, and DFNB35) have previously been mapped to the long arm of chromosome 14. The critical region for DFNA53 contains the gene for DFNA9 but does not overlap with the regions for DFNB5, DFNA23, or DFNB35. Screening of the COCH gene (DFNA9), BOCT, EFS, and HSPC156 within the DFNA53 interval did not identify the cause for deafness in this family. CONCLUSIONS: Identifying the DFNA53 locus is the first step in isolating the gene responsible for hearing loss in this large multigeneration Chinese family.

Mutational spectrum in Usher syndrome type II.

Usher syndrome type II is an autosomal recessive disorder characterized by moderate to severe hearing impairment and progressive visual loss due to retinitis pigmentosa (RP). We carried out a mutation screening of the USH2A gene in 88 probands with Usher syndrome type II to determine the frequency of USH2A mutations as a cause for USH2. Six mutations, including 2299delG, 921-922insCAGC, R334W, N346H, R626X, and N357T were identified, with 2299delG mutation being the most frequent (16.5% of alleles), accounting for 77.5% of the pathologic alleles. Thirty-five percent (31/88) of the probands had a USH2A mutation. Nine of them carried two pathogenic mutations: six cases were homozygotes and three were compound heterozygotes. Twenty-two probands (25%) were found to carry only single USH2A mutations. One new missense mutation (N357T) occuring within the laminin N-terminal (type VI) domain of usherin was identified. Eight polymorphisms were found, five of which are novel. Our data support the view that the 2299delG is the most common mutation in USH2A.

USH1C: a rare cause of USH1 in a non-Acadian population and a founder effect of the Acadian allele.

Usher syndrome (USH) is characterized by the associated findings of hearing loss and retinitis pigmentosa (RP), leading to progressive loss of vision. Three forms of USH can be distinguished clinically. In the most severe form, USH1, profound congenital deafness is associated with vestibular dysfunction and RP. To determine the frequency of USH1C mutations as a cause for USH1, 128 probands with Usher syndrome type 1 including seven from Acadian and 121 from non-Acadian populations were systematically screened for mutations in USH1C using a combined single-strand conformational polymorphisms (SSCP)/heteroduplex and sequencing method. All seven Acadian USH1 patients were found to be homozygous for both the 216G>A mutation and the 9-repeat VNTR which characterizes the Acadian allele, confirming previous evidence for a founder effect by haplotype analysis. However, USH1C mutations were identified in only two non-Acadian USH1 probands (1.65%) including one from Pakistan who was homozygous for a 238-239insC mutation and one from Canada was also homozygous for the Acadian allele. The low prevalence of USH1C mutations in the present study suggests that the high prevalence of the 238-239insC in Germany may reflect a founder effect. Comparison of the affected haplotypes in the Canadian patient with the Acadian USH1 patients yielded evidence for a founder effect. Our data suggest that USH1C is a relatively rare form of USH1 in non-Acadian populations and that in addition to the 216G>A Acadian mutation, the 238-239insC mutation appears to be common in some populations.

A novel locus for autosomal dominant non-syndromic deafness (DFNA41) maps to chromosome 12q24-qter.

We have studied 36 subjects in a large multigenerational Chinese family that is segregating for an autosomal dominant adult onset form of progressive non-syndromic hearing loss. All affected subjects had bilateral sensorineural hearing loss involving all frequencies with some significant gender differences in initial presentation. After excluding linkage to known loci for non-syndromic deafness, we used the Center for Inherited Disease Research (CIDR) to test for 351 polymorphic markers distributed at approximately 10 cM intervals throughout the genome. Analysis of the resulting data provided evidence that the locus designated DFNA41 maps to a 15 cM region on chromosome 12q24.32-qter, proximal to the marker D12S1609. A maximum two point lod score of 6.56 at theta=0.0 was obtained for D12S343. This gene is distal to DFNA25, a previously identified locus for dominant adult onset hearing loss that maps to 12q21-24. Positional/functional candidate genes in this region include frizzled 10, epimorphin, RAN, and ZFOC1.

Human angiopoietin gene expression is a marker for severity of pulmonary hypertension in patients undergoing pulmonary thromboendarterectomy.

OBJECTIVE: A consistent pathologic feature seen in lungs of patients with pulmonary hypertension from thromboembolic disease is hyperplasia of the media of pulmonary arterioles. The molecular factors responsible for these vessel wall changes are unknown. Angiopoietin-1 is a gene responsible for the formation of the media of blood vessels in utero. We hypothesized that aberrant expression of the angiopoietin-1 gene in the adult lung would be a major contributing factor in the development of pulmonary hypertension. METHODS: From April 1999 to March 2000, a total of 35 patients (18 men, 17 women, mean age 52 years) with pulmonary hypertension and pulmonary vascular resistance ranging from 407 to 2006 dynes x sec x cm(-5) underwent pulmonary endarterectomy at our institution. Before cardiopulmonary bypass, lung biopsy specimens were taken from each patient. Biopsy specimens were also obtained from 10 patients (5 women, 5 men, mean age 55 years) undergoing lung resection for causes other than pulmonary hypertension. All specimens were blindly scored by a pathologist for degree of medial hyperplasia. Quantitative reverse transcriptase-polymerase chain reaction, Western blot, and immunohistochemistry were used to quantitate angiopoietin-1 messenger RNA and protein in each sample. RESULTS: Lung specimens from all patients with pulmonary hypertension demonstrated up-regulation of angiopoietin-1 at the messenger RNA level. The degree of angiopoietin-1 transcription was directly proportional to the preoperative pulmonary vascular resistance and medial wall hyperplasia/hypertrophy in each patient. By immunohistochemistry, angiopoietin-1 protein was confined to the media of pulmonary arterioles. Lung biopsy specimens from patients without pulmonary hypertension had no detectable expression of angiopoietin-1 at the messenger RNA or protein level. CONCLUSION: Angiopoietin-1, a gene responsible for vessel development in the embryonic lung, is up-regulated in the lung parenchyma of patients with pulmonary hypertension. The level of expression of angiopoietin-1 at messenger RNA and protein levels correlates to the severity of pulmonary hypertension in patients with thromboembolic disease and serves as a target for strategies to treat this disease.

Yeast rab GTPase-activating protein Gyp1p localizes to the Golgi apparatus and is a negative regulator of Ypt1p.

A family of related proteins in yeast Saccharomyces cerevisiae is known to have in vitro GTPase-activating protein activity on the Rab GTPases. However, their in vivo function remains obscure. One of them, Gyp1p, acts on Sec4p, Ypt1p, Ypt7p, and Ypt51p in vitro. Here, we present data to reveal its in vivo substrate and the role that it plays in the function of the Rab GTPase. Red fluorescent protein-tagged Gyp1p is concentrated on cytoplasmic punctate structures that largely colocalize with a cis-Golgi marker. Subcellular fractionation of a yeast lysate confirmed that Gyp1p is peripherally associated with membranes and that it cofractionates with Golgi markers. This localization suggests that Gyp1p may only act on Rab GTPases on the Golgi. A gyp1Delta strain displays a growth defect on synthetic medium at 37 degrees C. Overexpression of Ypt1p, but not other Rab GTPases, strongly inhibits the growth of gyp1Delta cells. Conversely, a partial loss-of-function allele of YPT1, ypt1-2, can suppress the growth defect of gyp1Delta cells. Furthermore, deletion of GYP1 can partially suppress growth defects associated with mutants in subunits of transport protein particle complex, a complex that catalyzes nucleotide exchange on Ypt1p. These results establish that Gyp1p functions on the Golgi as a negative regulator of Ypt1p.