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PubMed2025

Exploring depression treatment response by using polygenic risk scoring across diverse populations.

Treatment-resistant depression (TRD), usually defined as limited or no response to at least two antidepressants, occurs in approximately one-third of individuals diagnosed with major depressive disorder (MDD). Studies of individuals of European ancestry highlight a genetic overlap between TRD and MDD. We analyzed two large and diverse biobanks, the UCLA ATLAS Community Health Study (ATLAS) and the All of Us Research Program (AoU), to test for associations between a polygenic score for major depression (MDD-PGS) and TRD. Compared to treatment responders, TRD individuals have higher MDD-PGS across all ancestries. MDD-PGS was significantly associated with response to selective serotonin reuptake inhibitors in individuals of European and Hispanic/Latin American genetic ancestries in both biobanks. In AoU, a decreased MDD-PGS was observed in response to tricyclics or serotonin modulators in individuals of European American ancestry and in response to serotonin and norepinephrine reuptake inhibitors in individuals of African American ancestry. ATLAS found that MDD-PGS showed lower odds of responding to atypical agents than did TRD in MDD-affected individuals belonging to the Hispanic/Latin American group, MDD-PGS was associated with atypical agents. Overall, by leveraging larger sample sizes from two diverse biobanks, we provide new insights into antidepressant response and treatment specificity for MDD in individuals of diverse genetic ancestries.

Adult↗

PubMed2025

Treatment-resistant depression: role of genetic factors in the perspective of clinical stratification and treatment personalisation.

Treatment-resistant depression (TRD) is associated with chronic depression, suicidal behaviours, and reduced quality of life. TRD has a demonstrated genetic component, estimated around 8% based on common genetic variation in unrelated individuals. However, only six genome-wide association studies of TRD were published, and no replicated signals at locus or gene level have been identified; furthermore, apparently opposite results were reported in terms of genetic overlap between TRD and other traits. Other than limited power, an important issue of previous studies was the scarce consideration of TRD heterogeneity, as TRD likely comprises different groups and talking about TRDs could be more appropriate. This review points out important issues in the definition of TRD and differences across samples included in previous studies, which can be partly responsible for the inconsistency across results. Different definitions of TRD should not be expected to have similar genetic profiles, and the whole TRD group can partitioned into subgroups, based on clinical and biological features, to increase reproducibility, as exemplified by recent findings. This can be a key factor to develop/repurpose targeted treatments, or simply to aid a more personalised prescription of available medications compared to current clinical practice, that is largely concentrated on the prescription of a limited number of antidepressants compared to those available.

Humans↗

PubMed2005

Genetic correlation between the free-choice oral consumption of nicotine and alcohol in C57BL/6JxC3H/HeJ F2 intercross mice.

Previous studies in humans have demonstrated a high co-morbidity between alcoholism and smoking. This co-morbidity between alcohol and nicotine dependence can be attributed, in part, to common genetic factors. In rodents, behavioral and physiological responses to alcohol and nicotine also appear to share common genetic influences. In this report, the genetic correlation between free-choice oral nicotine and oral alcohol consumption was evaluated using an ascending two-bottle choice paradigm in C57BL/6xC3H/HeJ F2 intercross mice. For all concentrations of nicotine (25, 50, and 100 microg/ml) and alcohol (3, 6, and 10%) tested, nicotine consumption was significantly correlated with alcohol consumption. Nicotine consumption at the highest nicotine concentration tested (100 microg/ml) showed low, but significant, correlations with the number of [3H]-cytisine binding sites in the hippocampus (r=0.307) and the number of [125I]-alpha-bungarotoxin binding sites in the cortex (r=-0.328). No significant correlations between alcohol consumption and the number of either [3H]-cytisine or [125I]-alpha-bungarotoxin binding sites was observed. A polymorphism in the nicotinic receptor alpha4 subunit gene, Chrna4, showed a trend with nicotine consumption and a significant association with alcohol consumption in female but not male mice. These results indicate that common genetic factors influence nicotine and alcohol consumption in mice. However, neither individual differences in the expression of [3H]-cytisine or [125I]-alpha-bungarotoxin binding nicotinic receptors nor the polymorphism in Chrna4 likely contribute to the genetic overlap that influences the consumption of both of these drugs of abuse in C57BL/6xC3H/HeJ F2 mice.

Alcohol Drinking↗

PubMed2005

Microsatellite analysis reveals genetic structure of Leishmania tropica.

The current rapid spread of leishmaniases caused by Leishmania tropica and the complexity of its clinical spectrum call for this parasite's epidemiological and evolutionary investigation. Evaluation of its population structure by isoenzyme electrophoresis and previous molecular biological analysis has proved difficult. In this study, we used 21 microsatellite loci to type 117 strains from different African and Asian locations. Eighty-one different genotypes were found. A genetic bottleneck supported by a gradient in the number of alleles and consistent with the geographical structure of the Middle East suggests an African origin of this species. A Bayesian approach identified 10 genetic clusters that correlated predominantly with geographical origin. The strains in the 'Asia' cluster form a very heterogeneous sub-population, with a varied but inter-related genotype that is geographically very widely dispersed and consistent with anthroponotic transmission of the parasite. The other nine clusters were more homogenous. The propagation of L. tropica appears to be predominantly clonal. In Africa and the Middle East, anthroponotic and zoonotic systems of distribution may contribute to the development of overlapping, genetically distinct populations of L. tropica.

Africa↗

PubMed2002

Cardiocutaneous syndromes and associations.

UNLABELLED: Multiple cardiocutaneous syndromes and associations are described and reviewed with the emphasis on syndromes that are likely first to be recognized by dermatologists, thereby creating awareness of potential significant cardiovascular disease. Multiple lentigines syndrome, the Carney complex, and Marfan syndrome are examples of syndromes with embryologic and genetic overlap between the cardiac and cutaneous systems. An exhaustive, complete listing of every known disorder or syndrome with combined cardiac and cutaneous findings is beyond the scope of this review. However, all the common associations, both acquired and inherited, including connective tissue, autoimmune, infiltrative, and endocrine disorders are discussed. Because of the serious nature of many of the cardiac defects, early recognition of these conditions by dermatologists and appropriate referrals to colleagues is essential; in addition, when appropriate, genetic counseling is recommended for known heritable disorders. LEARNING OBJECTIVE: At the conclusion of this learning activity, participants should be familiar with the embryology of the neural crest, specifically the development of melanocytes and the heart with its vessels, leading to shared abnormalities of the two systems; the major syndromes and associations producing both cutaneous changes, especially of the pigment systems, and cardiovascular abnormalities; the role of the dermatologist in recognizing these changes; and the need to be cognizant and alert in helping screen for associated systemic disease.

Cardiovascular Diseases↗

PubMed2002

Subvalvular pulmonary stenosis, demyelination and myelodysplasia with monosomy 7.

We report a 23-year-old male with subvalvular pulmonary stenosis (PS) presenting with concurrent acute demyelinating neuropathy and myelodysplasia with monosomy 7. There was no stigmata of Noonan syndrome or neurofibromatosis, nor any family history of cardiac or hematologic disorders. There are 40 reported pediatric cases of Noonan syndrome with subvalvular PS that developed leukemia, over two-thirds with monosomy 7. There is also a genetic overlap between Noonan syndrome and neurofibromatosis, which is also closely associated with demyelination and leukemia. The importance of recognition of rare clinical syndromes that may predispose to leukemia is discussed.

Adult↗

PubMed2025

Genetic relationships between systemic lupus erythematosus and a positive antinuclear antibody test in the absence of autoimmune disease.

OBJECTIVE: We defined the genetic factors associated with a positive ANA test (ANA+) in the absence of autoimmune disease and tested the association with SLE. METHODS: Using a case-control design, we performed a genome-wide association study (GWAS) in individuals of European ancestry without an autoimmune disease who had ANA tested as part of clinical care from DNA biobanks linked to de-identified electronic medical records: BioVU and Electronic Medical Records and Genomics. GWAS results were meta-analysed and single nucleotide polymorphism (SNP) heritability was calculated. A polygenic risk score (PRS) for ANA+ and for SLE was constructed and compared in patients with SLE, ANA+ and ANA negative (ANA-) individuals without autoimmune disease and general controls who never had ANA testing performed. RESULTS: A total of 7287 individuals of European ancestry were included in the meta-analyses (2169 ANA+ and 5118 ANA-); an SNP upstream of the TSBP1 in the HLA locus (rs1967688) was associated with ANA+ (p=4.84×10-8). SNP heritability for ANA+ was low (h2 SNP= 0.04), and the PRS for ANA+ was not significantly different in ANA+ and ANA- individuals. In contrast, the PRS for SLE was significantly higher in SLE compared with ANA+ individuals (p<2.2×10-16) but did not differ among ANA+, ANA- and general control groups (p=0.17). CONCLUSIONS: ANA+ occurring in the absence of autoimmune disease has a genetic association with the HLA region, but overall heritability is low. In addition, few SLE-associated SNPs were associated with ANA+, and the PRS for SLE was not associated with ANA+, indicating limited genetic overlap.

Humans↗

PubMed2026

Expanding the TBL1XR1 Disease Spectrum: Generalized Dystonia Associated with a New Genetic Variant.

BACKGROUND: A growing number of identified genes increasingly reveal genetic overlaps between neurodevelopmental disorders and combined dystonia syndromes. CASE REPORT: We report a 61-year-old man with a neurodevelopmental disorder, mild ataxic signs and generalized dystonia who had been misdiagnosed with cerebral palsy for 40 years. Whole-exome sequencing identified a novel heterozygous pathogenic frameshift variant in TBL1XR1. DISCUSSION: TBL1XR1 variants are classically associated with Pierpont syndrome and autism spectrum disorder. Although movement disorders have been reported, this case suggests generalized dystonia as a possible additional manifestation. It highlights the value of retrospective genetic phenotyping and next-generation sequencing in adults with long-standing neurodevelopmental diagnoses.

Humans↗

PubMed1999

The LQT syndromes--current status of molecular mechanisms.

Our knowledge on the molecular genetics of inherited cardiac arrhythmias is very recent in comparison to the advances of genetics achieved in other inherited cardiac disorders. This is related to the high mortality and early disease onset of these arrhythmias resulting in mostly small nucleus families. Thus, traditional genetic linkage studies that are based on the genetic information obtained from large multi-generation families were made difficult. In 1991, the first chromosomal locus for congenital long-QT (LQT) syndrome was identified on chromosome 11p15.5 (LQT1 locus) by linkage analysis. Meanwhile, the disease-causing gene at the LQT1 locus (KCNQ1), a gene encoding a K+ channel subunit of the IKs channel, and three other, major genes, all encoding cardiac ion channel components, have been identified. Taken together, LQT syndrome turned out to be a heterogeneous channelopathy. Moreover, the power of linkage studies to reveal the genetic causes of the LQT syndrome was also important to identify unknown but fundamental channel components that contribute to the ion currents tuning ventricular repolarization. In-vitro expression of the altered ion channel genes demonstrated in each case that the altered ion channel function produces prolongation of the action potential and thus the increasing propensity to ventricular tachyarrhythmias. Since these ion channels are pharmacological targets of many antiarrhythmic (and other) drugs, individual and potentially deleterious drug responses may be related to genetic variation in ion channel genes. Very recently, also in acquired LQT syndrome, which is a frequent clinical disorder in cardiology a genetic basis has been proposed in part since mutations in LQT genes have been specifically found. The discovery of ion channel defects in LQT syndrome represents the major achievement in our understanding and implies potential therapeutic options. The knowledge of the genomic structure of the LQT genes now offers the possibility to detect the underlying genetic defect in 80-90% of all patients. With this specific information, containing the type of ion channel (Na+ versus K+ channel) and electrophysiological alteration by the mutation (loss-of-function versus change-of-function mutation), gene-directed, elective drug therapies have been initiated in genotyped LQT patients. Based on preliminary data, that were supported by in vitro studies, this approach may be useful in recompensating the characteristic phenotypes in some LQT patients. Mutation detection is a new diagnostic tool which may become of more increasing importance in patients with a normal QTc or just a borderline prolongation of the QTc interval at presentation. These patients represent approximately 40% of all familial cases. Moreover, LQT3 syndrome and idiopathic ventricular fibrillation are allelic disorders and genetically overlap. In both mutations in the LQT3 gene SCN5A encoding the Na+ channel alpha-subunit for INa have been reported. Thus, the clinical nosology of inherited arrhythmias may be reconsidered after elucidation of the underlying molecular bases. Meanwhile, genotype-phenotype correlations in large families are on the way to evaluate intergene, interfamilial, and intrafamilial differences in the clinical phenotype reflecting gene specific, gene-site specific, and individual consequences of a given mutation. LQT syndrome is phenotypically heterogeneous due to the reduced penetrance and variable expressivity associated with the mutations. This paper discusses the current data on molecular genetics and genotype-phenotype correlations and the implications for diagnosis and treatment.

Chromosome Mapping↗

PubMed2001

Late onset white matter disease in peroxisome biogenesis disorder.

OBJECTIVE: To report late onset cerebral white matter disease as a distinctive phenotype in peroxisome biogenesis disorder (PBD). BACKGROUND: There is phenotypic and genetic overlap among the PBD known as Zellweger syndrome (ZS), infantile Refsum disease (IRD), and neonatal adrenoleukodystrophy (NALD). Distinctive external features are variable among these three disorders, and neurologic deficit has its onset at birth or in infancy. In a structured follow-up cohort of 25 patients with PBD, not including ZS, three patients had an unusual pattern of cerebral white matter disease with onset past the age of 1, not conforming to any of the classic PBD phenotypes. METHODS: Clinical phenotyping and follow-up, peroxisomal biochemical determinations in body fluids and fibroblasts, identification of affected PEX gene by genetic complementation in fibroblasts, and MRI studies. RESULTS: Two unrelated patients with PBD without distinctive external features had normal neurodevelopmental milestones during their first year, followed by rapid deterioration including severe hypotonic pareses, seizures, retinopathy, and deafness. A third patient initially diagnosed with IRD developed cerebral white matter degeneration in the third year of life, complicating the original diagnosis. MRI in all three patients showed cerebral demyelination with sparing of subcortical fibers and pronounced central cerebellar demyelination. CONCLUSIONS: Late-onset cerebral white matter disease may occur in PBD, either following IRD or following normal early development and in the absence of distinctive external features. Peroxisome biogenesis disorder should be included in the differential diagnosis of post-infantile onset of cerebral white matter disease

Brain↗

PubMed2005

Attention-deficit/hyperactivity disorder endophenotypes.

Attention-deficit/hyperactivity disorder (ADHD) is a highly heritable disorder with a multifactorial pattern of inheritance. For complex conditions such as this, biologically based phenotypes that lie in the pathway from genes to behavior may provide a more powerful target for molecular genetic studies than the disorder as a whole. Although their use in ADHD is relatively new, such "endophenotypes" have aided the clarification of the etiology and pathophysiology of several other conditions in medicine and psychiatry. In this article, we review existing data on potential endophenotypes for ADHD, emphasizing neuropsychological deficits because assessment tools are cost effective and relatively easy to implement. Neuropsychological impairments, as well as measures from neuroimaging and electrophysiological paradigms, show correlations with ADHD and evidence of heritability, but the familial or genetic overlap between these constructs and ADHD remains unclear. We conclude that these endophenotypes will not be a quick fix for the field but offer potential if careful consideration is given to issues of heterogeneity, measurement and statistical power.

Adoption↗

PubMed2026

Dissecting the shared genetic architecture between migraine subtypes and cardiovascular diseases: a multi-layered genomic analysis.

BACKGROUND: Epidemiological studies have linked migraine to an increased risk of cardiovascular disease (CVD); however, the shared genetic basis and putative causal relationships between migraine subtypes and cardiovascular traits remain poorly understood. METHODS: Leveraging large-scale GWAS summary statistics for migraine phenotypes (overall migraine, migraine with aura [MA], and migraine without aura [MO]) from FinnGen R12, along with seven cardiovascular diseases from publicly available consortia, we conducted a multi-layered genetic analysis. This integrative framework encompassed genetic correlation [linkage disequilibrium score regression (LDSC) and high-definition likelihood (HDL)], cross-trait meta-analysis (CPASSOC and PLACO), Bayesian colocalization, summary-data-based Mendelian randomization (SMR) using GTEx v8 eQTL data, and bidirectional two-sample Mendelian randomization (MR). RESULTS: Significant genetic correlations were identified between migraine and multiple cardiovascular traits, with hypertension and coronary artery disease (CAD) showing the most robust associations. MA exhibited broader genetic overlap with cardiovascular diseases than MO, including a notably stronger correlation with ischemic stroke, whereas MO demonstrated a stronger correlation with hypertension. Cross-trait meta-analysis identified 160 pleiotropic loci across 17 of 21 trait pairs. Colocalization analysis confirmed 32 loci harboring shared causal variants, mapped to 13 candidate genes, of which 7 (PHACTR1, LRP1, SOX7, ABO, FHOD3, MEI1, XKR6) were further validated by SMR as exhibiting tissue-specific regulatory effects. Among these, PHACTR1 displayed the broadest pleiotropic profile across migraine phenotypes and vascular diseases. After MR-PRESSO outlier removal, bidirectional MR identified 10 MR-supported associations, two of which (genetic liability to hypertension on overall migraine, and CAD on MA) survived Bonferroni correction, all free of detectable horizontal pleiotropy. Genetic liability to hypertension was associated with increased migraine risk (OR = 1.90, 95% CI 1.25-2.90, P = 2.64 × 10⁻³), atherosclerotic diseases showed subtype-specific effects (inverse for MO, positive for MA), and, in the reverse direction, migraine was associated with increased ischemic stroke risk. CONCLUSIONS: This study provides a comprehensive and systematic characterization of the shared genetic architecture between migraine subtypes and cardiovascular diseases. By identifying pleiotropic genes and bidirectional putative causal relationships with subtype-specific patterns, our findings carry implications for the development of targeted therapeutics and subtype-specific cardiovascular risk stratification.

Humans↗

PubMed2003

Genetic analysis of a functional GRIN2A promoter (GT)n repeat in bipolar disorder pedigrees in humans.

Hypofunction of glutamatergic neurotransmission has been hypothesized to underlie the pathophysiology of bipolar affective disorder, as well as schizophrenia. We examined the role of the N-methyl-D-aspartate receptor 2A subunit (GRIN2A) gene on 16p13.3, a region thought to be linked to bipolar disorder, (1) because in a prior study we identified a functional and polymorphic (GT)n repeat in the 5' regulatory region of the gene, with longer alleles showing lower transcriptional activity and an over representation in schizophrenia, and (2) because of the suggestion of a genetic overlap between affective disorder and schizophrenia. Family-based association tests detected a nominally significant preferential transmission of longer alleles in a panel of 96 multiplex bipolar pedigrees. These results support the hypothesis that a hypoglutamatergic state is involved in the pathogenesis of bipolar affective disorder.

Bipolar Disorder↗

PubMed2003

Corticobasal degeneration: selected developments.

Corticobasal degeneration (CBD) is now classified as a four-repeat tauopathy. The presence of neuronal and glial tau-immunoreactive lesions is critical to the pathological diagnosis. It is increasingly recognised that a variety of clinical phenotypes can occur as a consequence of this pathological state and that several other pathological conditions may be associated with the perceptuo-motor syndrome first associated with the pathological features of CBD (now referred to as the corticobasal syndrome). The high rate of diagnostic inaccuracy must be considered when interpreting previous literature dealing with cases presumed to be CBD. There is considerable clinical, pathological, and genetic overlap between CBD and progressive supranuclear palsy (PSP); however, the etiological and pathogenetic relationships between the two remain uncertain. There are reasons to believe that these diseases could be different phenotypes of a single process. Even if they are eventually found to be distinct disorders, treatments that alter the progression of one may have similar ameliorative effects on the other. Each of these issues are discussed in this selective review of CBD.

Diagnosis, Differential↗

PubMed2001

Overdominant epistatic loci are the primary genetic basis of inbreeding depression and heterosis in rice. I. Biomass and grain yield.

To understand the genetic basis of inbreeding depression and heterosis in rice, main-effect and epistatic QTL associated with inbreeding depression and heterosis for grain yield and biomass in five related rice mapping populations were investigated using a complete RFLP linkage map of 182 markers, replicated phenotyping experiments, and the mixed model approach. The mapping populations included 254 F(10) recombinant inbred lines derived from a cross between Lemont (japonica) and Teqing (indica) and two BC and two testcross hybrid populations derived from crosses between the RILs and their parents plus two testers (Zhong 413 and IR64). For both BY and GY, there was significant inbreeding depression detected in the RI population and a high level of heterosis in each of the BC and testcross hybrid populations. The mean performance of the BC or testcross hybrids was largely determined by their heterosis measurements. The hybrid breakdown (part of inbreeding depression) values of individual RILs were negatively associated with the heterosis measurements of their BC or testcross hybrids, indicating the partial genetic overlap of genes causing hybrid breakdown and heterosis in rice. A large number of epistatic QTL pairs and a few main-effect QTL were identified, which were responsible for >65% of the phenotypic variation of BY and GY in each of the populations with the former explaining a much greater portion of the variation. Two conclusions concerning the loci associated with inbreeding depression and heterosis in rice were reached from our results. First, most QTL associated with inbreeding depression and heterosis in rice appeared to be involved in epistasis. Second, most ( approximately 90%) QTL contributing to heterosis appeared to be overdominant. These observations tend to implicate epistasis and overdominance, rather than dominance, as the major genetic basis of heterosis in rice. The implications of our results in rice evolution and improvement are discussed.

Breeding↗

PubMed2006

Biometrical genetic analysis of luteovirus transmission in the aphid Schizaphis graminum.

The aphid Schizaphis graminum is an important vector of the viruses that cause barley yellow dwarf disease. We studied the genetic architecture of virus transmission by crossing a vector and a non-vector genotype of S. graminum. F1 and F2 hybrids were generated, and a modified line-cross biometrical analysis was performed on transmission phenotype of two of the viruses that cause barley yellow dwarf: Cereal yellow dwarf virus (CYDV)-RPV and Barley yellow dwarf virus (BYDV)-SGV. Our aims were to (1) determine to what extent differences in transmission ability between vectors and non-vectors is due to net additive or non-additive gene action, (2) estimate the number of loci that determine transmission ability and (3) examine the nature of genetic correlations between transmission of CYDV-RPV and BYDV-SGV. Only additive effects contributed significantly to divergence in transmission of both CYDV-RPV and BYDV-SGV. For each luteovirus, Castle-Wright's estimator for the number of effective factors segregating for transmission phenotype was less than one. Transmission of CYDV-RPV and BYDV-SGV was significantly correlated in the F2 generation, suggesting that there is a partial genetic overlap for transmission of these luteoviruses. Yet, 63% of the F2 genotypes transmitted CYDV-RPV and BYDV-SGV at significantly different rates. Our data suggest that in S. graminum, the transmission efficiency of both CYDV-RPV and BYDV-SGV is regulated by a major gene or set of tightly linked genes, and the transmission efficiency of each virus is influenced by a unique set of minor genes.

Animals↗

PubMed2005

Toward localizing genes underlying cerebral asymmetry and mental health.

Genome investigations of autism, attention deficit hyperactivity disorder (ADHD), and dyslexia suggest possible genetic overlap. Atypical cerebral asymmetry (ACA), the absence of the left hemisphere dominance for language, may be a shared phenotype due to genes located in regions of overlap. A binomal test is used to evaluate whether linked regions overlap more than expected by chance for 15 genome-wide scans in autism, ADHD, and dyslexia. Significant evidence of linkage overlap (P = 10(-7)) is seen for autism, ADHD, and dyslexia for seven chromosomal regions (2p11-12, 5p13, 7q22-33, 9q33-34, 13q22, 16p13, and 17p11-q11). Linkage analysis of ACA and molecular markers for 270 sibling pairs with ADHD is conducted using the Haseman-Elston statistic. Linkage analysis supports ACA as a shared phenotype with risk genes located on 9q33-34 or 16p13 (P < 0.004). Further support stems from the overlap of these regions in schizophrenia, bipolar illness, specific language impairment (SLI), and handedness, all traits associated with ACA. Autism, ADHD, and dyslexia share regions of linkage overlap and ACA may be a shared phenotype for such genes similar to HLA in autoimmune disease. Because ACA is associated with certain aspects of creativity, such risk genes may also be enhancer genes for creativity.

Attention Deficit Disorder with Hyperactivity↗

PubMed1998

Isolation of yeast mutants defective for localization of vacuolar vital dyes.

An application of flow cytometric sorting is used for isolation of Saccharomyces cerevisiae mutants that mislocalize vacuolar vital dyes. This screen is based on the ability of a lipophilic styryl compound, N-(3-triethylammoniumpropyl)-4-(6-(4-(diethylamino)phenyl)hexatrie nyl )pyridinium dibromide (FM4-64), to label endocytic intermediates from the plasma membrane to the vacuole membrane at 15 degreesC. Cells stained at 15 degreesC for both FM4-64 and carboxydichlorofluorescein diacetate (a vacuolar luminal vital stain), had a pronounced shift in red/green fluorescence from cells stained at 30 degrees or 38 degreesC. Flow cytometric selection based on this characteristic shift allowed the isolation of 16 mutants. These comprised 12 complementation groups, which we have designated SVL for styryl dye vacuolar localization. These groups were put into three classes. Class I mutants contain very large vacuoles; class II mutants have very fragmented vacuoles; and class III mutants show the strongest svl phenotype with punctate/diffuse FM4-64 staining. Limited genetic overlap was observed with previously isolated mutants, namely svl2/vps41, svl6/vps16, and svl7/fab1. The remaining svl mutants appear to represent novel genes, two of which showed temperature-sensitive vacuole staining morphology. Another mutant, svl8, displayed defects in uptake and sorting of phosphatidylcholine and phosphatidylethanolamine. Our flow cytometric strategy may be useful for isolation of other mutants where mislocalization of fluorescent compounds can be detected.

Biological Transport, Active↗