共查询到20条相似文献,搜索用时 381 毫秒
1.
Yuki Miyasaka Sari Suzuki Yasuhiro Ohshiba Kei Watanabe Yoshihiko Sagara Shumpei P. Yasuda Kunie Matsuoka Hiroshi Shitara Hiromichi Yonekawa Ryo Kominami Yoshiaki Kikkawa 《Experimental Animals》2013,62(4):333-346
The waltzer (v) mouse mutant harbors a mutation in Cadherin 23
(Cdh23) and is a model for Usher syndrome type 1D, which is
characterized by congenital deafness, vestibular dysfunction, and prepubertal onset of
progressive retinitis pigmentosa. In mice, functionally null Cdh23
mutations affect stereociliary morphogenesis and the polarity of both cochlear and
vestibular hair cells. In contrast, the murine Cdh23ahl
allele, which harbors a hypomorphic mutation, causes an increase in susceptibility to
age-related hearing loss in many inbred strains. We produced congenic mice by crossing
mice carrying the v niigata (Cdh23v-ngt) null
allele with mice carrying the hypomorphic Cdh23ahl allele on
the C57BL/6J background, and we then analyzed the animals’ balance and hearing phenotypes.
Although the
Cdh23v-ngt/ahl
compound heterozygous mice exhibited normal vestibular function, their hearing ability was
abnormal: the mice exhibited higher thresholds of auditory brainstem response (ABR) and
rapid age-dependent elevation of ABR thresholds compared with
Cdh23ahl/ahl
homozygous mice. We found that the stereocilia developed normally but were progressively
disrupted in
Cdh23v-ngt/ahl mice.
In hair cells, CDH23 localizes to the tip links of stereocilia, which are thought to gate
the mechanoelectrical transduction channels in hair cells. We hypothesize that the
reduction of Cdh23 gene dosage in
Cdh23v-ngt/ahl mice
leads to the degeneration of stereocilia, which consequently reduces tip link tension.
These findings indicate that CDH23 plays an important role in the maintenance of tip links
during the aging process. 相似文献
2.
The human ortholog of the gene responsible for audiogenic seizure susceptibility in Frings and BUB/BnJ mice (mouse gene symbol Mass1) recently was shown to underlie Usher syndrome type IIC (USH2C). Here we report that the Mass1frings mutation is responsible for the early onset hearing impairment of BUB/BnJ mice. We found highly significant linkage of Mass1 with ABR threshold variation among mice from two backcrosses involving BUB/BnJ mice with mice of strains CAST/EiJ and MOLD/RkJ. We also show an additive effect of the Cdh23 locus in modulating the progression of hearing loss in backcross mice. Together, these two loci account for more than 70% of the total ABR threshold variation among the backcross mice at all ages. The modifying effect of the strain-specific Cdh23ahl variant may account for the hearing and audiogenic seizure differences observed between Frings and BUB/BnJ mice, which share the Mass1frings mutation. During postnatal cochlear development in BUB/BnJ mice, stereocilia bundles develop abnormally and remain immature and splayed into adulthood, corresponding with the early onset hearing impairment associated with Mass1frings. Progressive base-apex hair cell degeneration occurs at older ages, corresponding with the age-related hearing loss associated with Cdh23ahl. The molecular basis and pathophysiology of hearing loss suggest BUB/BnJ and Frings mice as models to study cellular and molecular mechanisms underlying USH2C auditory pathology. 相似文献
3.
Xu Han Ruli Ge Gang Xie Ping Li Xin Zhao Lixiang Gao Heng Zhang Oumei Wang Fei Huang Fengchan Han 《ASN neuro》2015,7(1)
A/J and C57BL/6 J (B6) mice share a mutation in Cdh23 (ahl allele) and are characterized by age-related hearing loss. However, hearing loss occurs much earlier in A/J mice at about four weeks of age. Recent study has revealed that a mutation in citrate synthase (Cs) is one of the main contributors, but the mechanism is largely unknown. In the present study, we showed that A/J mice displayed more severe degeneration of hair cells, spiral ganglion neurons, and stria vascularis in the cochleae compared with B6 mice. Moreover, messenger RNA accumulation levels of caspase-3 and caspase-9 in the inner ears of A/J mice were significantly higher than those in B6 mice at 2 and 8 weeks of age. Immunohistochemistry localized caspase-3 expression mainly to the hair cells, spiral ganglion neurons, and stria vascularis in cochleae. In vitro transfection with Cs short hairpin RNA (shRNA) alone or cotransfection with Cs shRNA and Cdh23 shRNA significantly increased the levels of caspase-3 in an inner ear cell line (HEI-OC1). Finally, a pan-caspase inhibitor Z-VAD-FMK could preserve the hearing of A/J mice by lowering about 15 decibels of the sound pressure level for the auditory-evoked brainstem response thresholds. In conclusion, our results suggest that caspase-mediated apoptosis in the cochleae, which may be related to a Cs mutation, contributes to the early onset of hearing loss in A/J mice. 相似文献
4.
Akinori Kashio Akiko Amano Takashi Sakamoto Mitsuya Suzuki Tatsuya Yamasoba 《Biochemical and biophysical research communications》2009,390(3):394-2294
Using senescence marker protein 30 (SMP30)/gluconolactonase (GNL) knockout (KO) mice, which cannot synthesize vitamin C (VC), we examined whether modulating VC level affects age-related hearing loss (AHL). KO and wild-type (WT) C57BL/6 mice were given water containing 1.5 g/L VC [VC(+)] or 37.5 mg/L VC [VC(−)]. At 10 months of age, KO VC(−) mice showed significant reduction in VC level in the inner ear, plasma, and liver, increase in auditory brainstem response (ABR) thresholds, and decrease in the number of spiral ganglion cells compared to WT VC(−), WT VC(+), and KO VC(+) mice. There were no differences in VC level in the inner ear, ABR thresholds, or the number of spiral ganglion cells among WT VC(−), WT VC(+), and KO VC(+) mice. These findings suggest that VC depletion can accelerate AHL but that supplementing VC may not increase VC level in the inner ear or slow AHL in mice. 相似文献
5.
Ahl2, a second locus affecting age-related hearing loss in mice 总被引:7,自引:0,他引:7
Inbred mouse strains with age-related hearing loss (AHL) provide valuable models for studying the genetic basis of human presbycusis. Here we report the genetic mapping of a second AHL locus in mice (designated Ahl2) that is a major contributor to the 8- to 10-month difference in hearing loss onset times between NOD/LtJ and C57BL/6J mice. A whole-genome linkage scan of 110 progeny from a (C57BL/6JxNOD/LtJ)xNOD/LtJ backcross revealed statistically significant associations of ABR thresholds with markers on chromosome 5, with a peak lod score of 5.5 for D5Mit309. At 6 months of age, backcross progeny that inherited two copies of the recessive NOD/LtJ-derived allele at this locus (genotype ahl2/ahl2) exhibited ABR thresholds that were on average 26 decibels above those of heterozygous mice. Analysis of a (CAST/EixNOD/LtJ)xNOD/LtJ backcross, which segregates strain-specific alleles at both Ahl2 and the Ahl locus on chromosome 10, showed that the hearing loss attributable to Ahl2 is dependent on a predisposing Ahl genotype. The statistically significant effect of Ahl2 observed in crosses with NOD/LtJ was not seen in crosses involving three other strains with early onset AHL: A/J, BUB/BnJ, and SKH2/J. 相似文献
6.
7.
Nemoto M Morita Y Mishima Y Takahashi S Nomura T Ushiki T Shiroishi T Kikkawa Y Yonekawa H Kominami R 《Biochemical and biophysical research communications》2004,324(4):1283-1288
Genetic variation in humans probably plays a role in determining the range of individual susceptibility to age-related hearing loss (AHL), but no contributing loci have been identified because of the difficulties of dissecting complex traits in humans. This paper reports mapping of an AHL locus using a panel of consomic mice between C57BL/6J (B6) and MSM strains, which covered more than a half of chromosome sets. B6 strain exhibited AHL beginning at 10 months of age whereas MSM strain, derived from Japanese wild mice, had normal hearing throughout life. Individuals in the panel were examined with auditory brainstem response (ABR) at various months of age, revealing that one particular strain (B6-Chr17(MSM)) substituting the chromosome 17 with the MSM-derived one showed a prominent resistance, having still good hearing at 18 months of age. Subsequent mapping using 89 individuals in the cross between B6-Chr17(MSM) and B6 was performed, which showed a significant association of ABR thresholds with loci in the vicinity of D17Mit119. These results show a novel AHL-resistant locus, designated as Ahl3, on the chromosome 17. 相似文献
8.
9.
Morita Y Hirokawa S Kikkawa Y Nomura T Yonekawa H Shiroishi T Takahashi S Kominami R 《Biochemical and biophysical research communications》2007,355(1):117-121
A region in the vicinity of D17Mit119 on mouse chromosome 17 harbors a susceptibility gene, designated as Ahl3, to age-related hearing loss (AHL). We produced congenic lines of C57BL/6 background that substituted regions around D17Mit119 with MSM-derived ones, and examined auditory brainstem response (ABR) thresholds for their hearing capacity at 6 and 12months of age. Three congenic lines carrying the approximately 14-Mb region between D17Mit274 and D17Mit183 retained normal hearing at 12months of age whereas two congenic lines not carrying this region tended to lose hearing at that age. We also investigated noise-induced hearing loss (NIHL) in congenic lines at 1, 7 and 14days after exposure to the noise of 100dB for 1h. Most congenic mice carrying the 14-Mb region did not exhibit permanent threshold shift (PTS) whereas mice not carrying this region exhibited a strong tendency of PTS, indicating the role of Ahl3 in susceptibility to NIHL. These results indicate that Ahl3 exists within the 14-Mb region and affects not only AHL but also NIHL. 相似文献
10.
Noguchi Y Kurima K Makishima T de Angelis MH Fuchs H Frolenkov G Kitamura K Griffith AJ 《Genetics》2006,173(4):2111-2119
Dominant mutations of transmembrane channel-like gene 1 (TMC1) cause progressive sensorineural hearing loss in humans and Beethoven (Tmc1Bth/+) mice. Here we show that Tmc1Bth/+ mice on a C3HeB/FeJ strain background have selective degeneration of inner hair cells while outer hair cells remain structurally and functionally intact. Inner hair cells primarily function as afferent sensory cells, whereas outer hair cells are electromotile amplifiers of auditory stimuli that can be functionally assessed by distortion product otoacoustic emission (DPOAE) analysis. When C3H-Tmc1Bth/Bth is crossed with either C57BL/6J or DBA/2J wild-type mice, F1 hybrid Tmc1Bth/+ progeny have increased hearing loss associated with increased degeneration of outer hair cells and diminution of DPOAE amplitudes but no difference in degeneration of inner hair cells. We mapped at least one quantitative trait locus (QTL), Tmc1m1, for DPOAE amplitude on chromosome 2 in [(C/B)F1xC]N2-Tmc1Bth/+ backcross progeny, and three other QTL on chromosomes 11 (Tmc1m2), 12 (Tmc1m3), and 5 (Tmc1m4) in [(C/D)F1xC]N2-Tmc1Bth/+ progeny. The polygenic basis of outer hair cell degeneration in Beethoven mice provides a model system for the dissection of common, complex hearing loss phenotypes, such as presbycusis, that involve outer hair cell degeneration in humans. 相似文献
11.
Background
Although outer hair cells (OHCs) play a key role in cochlear amplification, it is not fully understood how they amplify sound signals by more than 100 fold. Two competing or possibly complementary mechanisms, stereocilia-based and somatic electromotility-based amplification, have been considered. Lacking knowledge about the exceptionally rich protein networks in the OHC plasma membrane, as well as related protein-protein interactions, limits our understanding of cochlear function. Therefore, we focused on finding protein partners for two important membrane proteins: Cadherin 23 (cdh23) and prestin. Cdh23 is one of the tip-link proteins involved in transducer function, a key component of mechanoelectrical transduction and stereocilia-based amplification. Prestin is a basolateral membrane protein responsible for OHC somatic electromotility.Results
Using the membrane-based yeast two-hybrid system to screen a newly built cDNA library made predominantly from OHCs, we identified two completely different groups of potential protein partners using prestin and cdh23 as bait. These include both membrane bound and cytoplasmic proteins with 12 being de novo gene products with unknown function(s). In addition, some of these genes are closely associated with deafness loci, implying a potentially important role in hearing. The most abundant prey for prestin (38%) is composed of a group of proteins involved in electron transport, which may play a role in OHC survival. The most abundant group of cdh23 prey (55%) contains calcium-binding domains. Since calcium performs an important role in hair cell mechanoelectrical transduction and amplification, understanding the interactions between cdh23 and calcium-binding proteins should increase our knowledge of hair cell function at the molecular level.Conclusion
The results of this study shed light on some protein networks in cochlear hair cells. Not only was a group of de novo genes closely associated with known deafness loci identified, but the data also indicate that the hair cell tip link interacts directly with calcium binding proteins. The OHC motor protein, prestin, also appears to be associated with electron transport proteins. These unanticipated results open potentially fruitful lines of investigation into the molecular basis of cochlear amplification. 相似文献12.
13.
Yoko Nakano Sung H. Kim Hyoung-Mi Kim Joel D. Sanneman Yuzhou Zhang Richard J. H. Smith Daniel C. Marcus Philine Wangemann Randy A. Nessler Botond Bnfi 《PLoS genetics》2009,5(8)
Hereditary hearing loss is one of the most common birth defects, yet the majority of genes required for audition is thought to remain unidentified. Ethylnitrosourea (ENU)–mutagenesis has been a valuable approach for generating new animal models of deafness and discovering previously unrecognized gene functions. Here we report on the characterization of a new ENU–induced mouse mutant (nmf329) that exhibits recessively inherited deafness. We found a widespread loss of sensory hair cells in the hearing organs of nmf329 mice after the second week of life. Positional cloning revealed that the nmf329 strain carries a missense mutation in the claudin-9 gene, which encodes a tight junction protein with unknown biological function. In an epithelial cell line, heterologous expression of wild-type claudin-9 reduced the paracellular permeability to Na+ and K+, and the nmf329 mutation eliminated this ion barrier function without affecting the plasma membrane localization of claudin-9. In the nmf329 mouse line, the perilymphatic K+ concentration was found to be elevated, suggesting that the cochlear tight junctions were dysfunctional. Furthermore, the hair-cell loss in the claudin-9–defective cochlea was rescued in vitro when the explanted hearing organs were cultured in a low-K+ milieu and in vivo when the endocochlear K+-driving force was diminished by deletion of the pou3f4 gene. Overall, our data indicate that claudin-9 is required for the preservation of sensory cells in the hearing organ because claudin-9–defective tight junctions fail to shield the basolateral side of hair cells from the K+-rich endolymph. In the tight-junction complexes of hair cells, claudin-9 is localized specifically to a subdomain that is underneath more apical tight-junction strands formed by other claudins. Thus, the analysis of claudin-9 mutant mice suggests that even the deeper (subapical) tight-junction strands have biologically important ion barrier function. 相似文献
14.
A major gene affecting age-related hearing loss is common to at least ten inbred strains of mice 总被引:12,自引:0,他引:12
Inbred strains of mice offer promising models for understanding the genetic basis of human presbycusis or age-related hearing loss (AHL). We previously mapped a major gene affecting AHL in C57BL/6J mice. Here, we show that the same Chromosome 10 gene (Ahl) is a major contributor to AHL in nine other inbred mouse strains-129P1/ReJ, A/J, BALB/cByJ, BUB/BnJ, C57BR/cdJ, DBA/2J, NOD/LtJ, SKH2/J, and STOCK760. F1 hybrids between each of these inbred strains and the normal-hearing inbred strain CAST/Ei retain good hearing, indicating that inheritance of AHL is recessive. To follow segregation of hearing loss, F1 hybrids were backcrossed to the parental strains with AHL. Auditory-evoked brain-stem response thresholds were used to assess hearing in more than 1500 N2 mice and analyzed as quantitative traits for linkage associations with Chromosome 10 markers. Highly significant linkage was found in all nine strain backcrosses, with the highest probability (LOD > 70) near the marker D10Mit112. This map position for Ahl is near the waltzer mutation (v) and the modifier of deaf waddler locus (mdfw), suggesting the possibility of allelism. Results from an intercross of C57BL/6J and NOD/LtJ mice indicate that the 6- to 10-month difference in AHL onset between these two strains is not due to allelic heterogeneity of the Ahl gene. 相似文献
15.
Yoko Nakano Sung H. Kim Hyoung-Mi Kim Joel D. Sanneman Yuzhou Zhang Richard J. H. Smith Daniel C. Marcus Philine Wangemann Randy A. Nessler Botond Bánfi 《PLoS genetics》2009,5(8)
Hereditary hearing loss is one of the most common birth defects, yet the majority of genes required for audition is thought to remain unidentified. Ethylnitrosourea (ENU)–mutagenesis has been a valuable approach for generating new animal models of deafness and discovering previously unrecognized gene functions. Here we report on the characterization of a new ENU–induced mouse mutant (nmf329) that exhibits recessively inherited deafness. We found a widespread loss of sensory hair cells in the hearing organs of nmf329 mice after the second week of life. Positional cloning revealed that the nmf329 strain carries a missense mutation in the claudin-9 gene, which encodes a tight junction protein with unknown biological function. In an epithelial cell line, heterologous expression of wild-type claudin-9 reduced the paracellular permeability to Na+ and K+, and the nmf329 mutation eliminated this ion barrier function without affecting the plasma membrane localization of claudin-9. In the nmf329 mouse line, the perilymphatic K+ concentration was found to be elevated, suggesting that the cochlear tight junctions were dysfunctional. Furthermore, the hair-cell loss in the claudin-9–defective cochlea was rescued in vitro when the explanted hearing organs were cultured in a low-K+ milieu and in vivo when the endocochlear K+-driving force was diminished by deletion of the pou3f4 gene. Overall, our data indicate that claudin-9 is required for the preservation of sensory cells in the hearing organ because claudin-9–defective tight junctions fail to shield the basolateral side of hair cells from the K+-rich endolymph. In the tight-junction complexes of hair cells, claudin-9 is localized specifically to a subdomain that is underneath more apical tight-junction strands formed by other claudins. Thus, the analysis of claudin-9 mutant mice suggests that even the deeper (subapical) tight-junction strands have biologically important ion barrier function. 相似文献
16.
Sari SUZUKI Masashi ISHIKAWA Takuya UEDA Yasuhiro OHSHIBA Yuki MIYASAKA Kazuhiro OKUMURA Michinari YOKOHAMA Choji TAYA Kunie MATSUOKA Yoshiaki KIKKAWA 《Experimental Animals》2015,64(3):241-251
The DBA/2J strain is a model for early-onset, progressive hearing loss in humans, as
confirmed in the present study. DBA/2J mice showed progression of hearing loss to
low-frequency sounds from ultrasonic-frequency sounds and profound hearing loss at all
frequencies before 7 months of age. It is known that the early-onset hearing loss of
DBA/2J mice is caused by affects in the ahl
(Cdh23ahl) and ahl8
(Fscn2ahl8) alleles of the cadherin 23 and fascin 2 genes,
respectively. Although the strong contributions of the
Fscn2ahl8 allele were detected in hearing loss at 8- and
16-kHz stimuli with LOD scores of 5.02 at 8 kHz and 8.84 at 16 kHz, hearing loss effects
were also demonstrated for three new quantitative trait loci (QTLs) for the intervals of
50.3–54.5, 64.6–119.9, and 119.9–137.0 Mb, respectively, on chromosome 5, with significant
LOD scores of 2.80–3.91 for specific high-frequency hearing loss at 16 kHz by quantitative
trait loci linkage mapping using a (DBA/2J × C57BL/6J) F1 × DBA/2J backcross
mice. Moreover, we showed that the contribution of Fscn2ahl8
to early-onset hearing loss with 32-kHz stimuli is extremely low and raised the
possibility of effects from the Cdh23ahl allele and another
dominant quantitative trait locus (loci) for hearing loss at this ultrasonic frequency.
Therefore, our results suggested that frequency-specific QTLs control early-onset hearing
loss in DBA/2J mice. 相似文献
17.
Qunfeng Cai Bo Wang Donald Coling Jian Zuo Jie Fang Shiming Yang Krystal Vera Bo Hua Hu 《PloS one》2014,9(12)
Various cochlear pathologies, such as acoustic trauma, ototoxicity and age-related degeneration, cause hearing loss. These pre-existing hearing losses can alter cochlear responses to subsequent acoustic overstimulation. So far, the knowledge on the impacts of pre-existing hearing loss caused by genetic alteration of cochlear genes is limited. Prestin is the motor protein expressed exclusively in outer hair cells in the mammalian cochlea. This motor protein contributes to outer hair cell motility. At present, it is not clear how the interference of prestin function affects cochlear responses to acoustic overstimulation. To address this question, a genetic model of prestin dysfunction in mice was created by inserting an internal ribosome entry site (IRES)-CreERT2-FRT-Neo-FRT cassette into the prestin locus after the stop codon. Homozygous mice exhibit a threshold elevation of auditory brainstem responses with large individual variation. These mice also display a threshold elevation and a shift of the input/output function of the distortion product otoacoustic emission, suggesting a reduction in outer hair cell function. The disruption of prestin function reduces the threshold shifts caused by exposure to a loud noise at 120 dB (sound pressure level) for 1 h. This reduction is positively correlated with the level of pre-noise cochlear dysfunction and is accompanied by a reduced change in Cdh1 expression, suggesting a reduction in molecular responses to the acoustic overstimulation. Together, these results suggest that prestin interference reduces cochlear stress responses to acoustic overstimulation. 相似文献
18.
Progressive sensorineural hearing loss is the most common form of acquired hearing impairment in the human population. It is also highly prevalent in inbred strains of mice, providing an experimental avenue to systematically map genetic risk factors and to dissect the molecular pathways that orchestrate hearing in peripheral sensory hair cells. Therefore, we ascertained hearing function in the inbred long sleep (ILS) and inbred short sleep (ISS) strains. Using auditory-evoked brain stem response (ABR) and distortion product otoacoustic emission (DPOAE) measurements, we found that ISS mice developed a high-frequency hearing loss at twelve weeks of age that progressed to lower frequencies by 26 weeks of age in the presence of normal endocochlear potentials and unremarkable inner ear histology. ILS mice exhibited milder hearing loss, showing elevated thresholds and reduced DPOAEs at the higher frequencies by 26 weeks of age. To map the genetic variants that underlie this hearing loss we computed ABR thresholds of 63 recombinant inbred stains derived from the ISS and ILS founder strains. A single locus was linked to markers associated with ISS alleles on chromosome 10 with a highly significant logarithm of odds (LOD) score of 15.8. The 2-LOD confidence interval spans ∼4 Megabases located at position 54–60 Mb. This locus, termed sensorineural hearing loss 1 (Snhl1), accounts for approximately 82% of the phenotypic variation. In summary, this study identifies a novel hearing loss locus on chromosome 10 and attests to the prevalence and genetic heterogeneity of progressive hearing loss in common mouse strains. 相似文献
19.
Morishita H Makishima T Kaneko C Lee YS Segil N Takahashi K Kuraoka A Nakagawa T Nabekura J Nakayama K Nakayama KI 《Biochemical and biophysical research communications》2001,284(1):142-149
Mice that lack caspase-3, which functions in apoptosis, were generated by gene targeting and shown to undergo hearing loss. The ABR threshold of the caspase-3(-/-) mice was significantly elevated compared to that of caspase-3(+/+) mice at 15 days of age and was progressively elevated further by 30 days. Distortion product otoacoustic emissions were not detectable in caspase-3(-/-) mice at 15 days of age. Caspase-3(-/-) mice exhibited marked degeneration of spiral ganglion neurons and a loss of inner and outer hair cells in the cochlea at 30 days of age, although no such changes were apparent at 15 days. The degenerating neurons manifested features, including cytoplasmic vacuolization, distinct from those characteristic of apoptosis. Spiral ganglion neurons and cochlear hair cells thus appear to require caspase-3 for survival but not for initial development. The mapping of both the human caspase-3 gene and the locus responsible for an autosomal dominant, nonsyndromic form of hearing loss (DFNA24) to chromosome 4q35 suggests that the caspase-3(-/-) mice may represent a model of this human condition. 相似文献
20.
Cdh1p, a substrate specificity factor for the cell cycle-regulated ubiquitin ligase, the anaphase-promoting complex/cyclosome (APC/C), promotes exit from mitosis by directing the degradation of a number of proteins, including the mitotic cyclins. Here we present evidence that Cdh1p activity at the M/G(1) transition is important not only for mitotic exit but also for high-fidelity chromosome segregation in the subsequent cell cycle. CDH1 showed genetic interactions with MAD2 and PDS1, genes encoding components of the mitotic spindle assembly checkpoint that acts at metaphase to prevent premature chromosome segregation. Unlike cdh1delta and mad2delta single mutants, the mad2delta cdh1delta double mutant grew slowly and exhibited high rates of chromosome and plasmid loss. Simultaneous deletion of PDS1 and CDH1 caused extensive chromosome missegregation and cell death. Our data suggest that at least part of the chromosome loss can be attributed to kinetochore/spindle problems. Our data further suggest that Cdh1p and Sic1p, a Cdc28p/Clb inhibitor, have overlapping as well as nonoverlapping roles in ensuring proper chromosome segregation. The severe growth defects of both mad2delta cdh1delta and pds1delta cdh1dDelta strains were rescued by overexpressing Swe1p, a G(2)/M inhibitor of the cyclin-dependent kinase, Cdc28p/Clb. We propose that the failure to degrade cyclins at the end of mitosis leaves cdh1delta mutant strains with abnormal Cdc28p/Clb activity that interferes with proper chromosome segregation. 相似文献