Genetic Analysis of RAB39B in an Early-Onset Parkinson's Disease Cohort.

Pathogenic variants in the gene encoding RAB39B, resulting in the loss of protein function, lead to the development of X-linked early-onset parkinsonism. The gene is located within a chromosomal region that is susceptible to genomic rearrangement, and while an increased dosage of RAB39B was previously associated with cognitive impairment, the potential role of dosage alterations in Parkinson's disease (PD) remains to be determined. This study aimed to investigate the contribution of the genetic variation in RAB39B to the development of early-onset PD. We performed gene dosage studies and sequence analysis in a cohort of 176 individuals with early-onset PD (age of onset ≤ 50 years) of unknown genetic etiology. An assessment of the copy number variation over both coding exons and the 3' untranslated region (UTR) of RAB39B did not identify any alterations in gene dosage. An analysis of the UTRs identified two male individuals carrying single, likely benign, nucleotide variants in the 3'UTR (chrX:154489749-A-G and chrX:154489197-T-G). Furthermore, one novel variant of uncertain significance was identified in the 5'UTR, 229 bp upstream of the start codon (chrX:154493802-C-T). In silico analyses predicted that this variant disrupts a highly conserved transcription factor binding site and could impact RAB39B expression. The results of this study do not support a significant role for genetic variation in RAB39B as contributing to early-onset PD but do highlight that additional molecular studies are required to determine the mechanisms regulating RAB39B expression and their association with the disease. Genetic investigations in larger parkinsonism/PD cohorts and longitudinal studies of individuals with cognitive impairment due to an altered dosage of RAB39B will be required to fully delineate the contribution of RAB39B to parkinsonism.

Distribution of Parkinson's disease associated RAB39B in mouse brain tissue.

Pathogenic variants in the gene encoding the small GTPase Ras analogue in Brain 39b (RAB39B) are associated with early-onset parkinsonism. In this study we investigated the expression and localization of RAB39B (RNA and protein) in mouse brain tissue to gain a better understanding of its normal physiological function(s) and role in disease.We developed novel resources, including monoclonal antibodies directed against RAB39B and mice with Rab39b knockout, and performed real-time PCR and western blot analysis on whole brain lysates. To determine the spatial localization of Rab39b RNA and protein, we performed in-situ hybridization and immunohistochemistry on fresh frozen and fixed brain tissue. Our results show that RAB39B is localized throughout the cortex, hippocampus and substantia nigra of mice throughout postnatal life. We found high levels of RAB39B within MAP2 positive cortical and hippocampal neurons, and TH positive dopaminergic neurons in the substantia nigra pars compacta.Our studies support and extend current knowledge of the localization of RAB39B. We validate RAB39B as a neuron-enriched protein and demonstrate that it is present throughout the mouse cortex and hippocampus. Further, we observe high levels in the substantia nigra pars compacta, the brain region most affected in Parkinson's disease pathology. The distribution of Rab39b is consistent with human disease associations with parkinsonism and cognitive impairment. We also describe and validate novel resources, including monoclonal antibodies directed against RAB39B and mice with Rab39b knockout, both of which are valuable tools for future studies of the molecular function of RAB39B.

Familial early onset Parkinson's disease caused by a homozygous frameshift variant in PARK7: Clinical features and literature update.

BACKGROUND: Bi-allelic mutations in PARK7 are a rare cause of autosomal recessive early onset Parkinson's disease (EO-PD). To date, 30 individuals harbouring 20 unique causative variants have been described. Understanding of the spectrum of clinical features and natural history of PARK7 mediated EO-PD remain limited. METHODS: We studied a family with three offspring, two of whom were affected with EO-PD. Family members underwent detailed clinical examination and DNA samples from both affected individuals and parents were analysed by exome sequencing. RESULTS: Two brothers of Iranian descent presented at age 29 years with Parkinsonism associated with high-pitched voice and hypomimia. The brothers were followed over a six and fifteen-year period and displayed typical levodopa responsive slowly-progressive Parkinsonism. A novel homozygous frameshift mutation in PARK7 [NM_007262.4:c.90dupG, p(Ile31Aspfs*2)] was identified. CONCLUSIONS: Here we report the clinical presentation and progression of EO-PD in brothers with a novel pathogenic PARK7 variant. We expand the clinical phenotype and provide an update of clinical and pathological features of the disorder.

Functional analysis of a hypomorphic allele shows that MMP14 catalytic activity is the prime determinant of the Winchester syndrome phenotype.

Winchester syndrome (WS, MIM #277950) is an extremely rare autosomal recessive skeletal dysplasia characterized by progressive joint destruction and osteolysis. To date, only one missense mutation in MMP14, encoding the membrane-bound matrix metalloprotease 14, has been reported in WS patients. Here, we report a novel hypomorphic MMP14 p.Arg111His (R111H) allele, associated with a mitigated form of WS. Functional analysis demonstrated that this mutation, in contrast to previously reported human and murine MMP14 mutations, does not affect MMP14's transport to the cell membrane. Instead, it partially impairs MMP14's proteolytic activity. This residual activity likely accounts for the mitigated phenotype observed in our patients. Based on our observations as well as previously published data, we hypothesize that MMP14's catalytic activity is the prime determinant of disease severity. Given the limitations of our in vitro assays in addressing the consequences of MMP14 dysfunction, we generated a novel mmp14a/b knockout zebrafish model. The fish accurately reflected key aspects of the WS phenotype including craniofacial malformations, kyphosis, short-stature and reduced bone density owing to defective collagen remodeling. Notably, the zebrafish model will be a valuable tool for developing novel therapeutic approaches to a devastating bone disorder.

Generation of RAB39B knockout isogenic human embryonic stem cell lines to model RAB39B-mediated Parkinson's disease.

Mutations in RAB39B are a known cause of X-linked early onset Parkinson's disease. Isogenic human embryonic stem cell lines carrying two independent deletions of RAB39B were generated using CRISPR/Cas9 genome editing tool. The deletions were confirmed by PCR and direct sequence analysis in two edited stem cell lines. Both cell lines showed pluripotency and displayed a normal karyotype. Further, they were able to form embryoid bodies in vitro, and express markers indicative of differentiation to the three germ layers.

The emerging role of Rab GTPases in the pathogenesis of Parkinson's disease.

The identification of pathogenic mutations in Ras analog in brain 39B (RAB39B) and Ras analog in brain 32 (RAB32) that cause Parkinson's disease (PD) has highlighted the emerging role of protein trafficking in disease pathogenesis. Ras analog in brain (Rab) Guanosine triphosphatase (GTPase) function as master regulators of membrane trafficking, including vesicle formation, movement along cytoskeletal networks, and membrane fusion. Recent studies have linked Rab GTPases with α-synuclein, Leucine-rich repeat kinase 2, and Vacuolar protein sorting 35, 3 key proteins in PD pathogenesis. In this review, we discuss the various RAB GTPases associated with PD, current progress in the research, and potential future directions. Investigations into the function of RAB GTPases will likely provide significant insight into the etiology of PD and identify novel therapeutic targets for a currently incurable disease. © 2018 International Parkinson and Movement Disorder Society.

ALPK3-deficient cardiomyocytes generated from patient-derived induced pluripotent stem cells and mutant human embryonic stem cells display abnormal calcium handling and establish that ALPK3 deficiency underlies familial cardiomyopathy.

AIMS: We identified a novel homozygous truncating mutation in the gene encoding alpha kinase 3 (ALPK3) in a family presenting with paediatric cardiomyopathy. A recent study identified biallelic truncating mutations of ALPK3 in three unrelated families; therefore, there is strong genetic evidence that ALPK3 mutation causes cardiomyopathy. This study aimed to clarify the mutation mechanism and investigate the molecular and cellular pathogenesis underlying ALPK3-mediated cardiomyopathy. METHODS AND RESULTS: We performed detailed clinical and genetic analyses of a consanguineous family, identifying a new ALPK3 mutation (c.3792G>A, p.W1264X) which undergoes nonsense-mediated decay in ex vivo and in vivo tissues. Ultra-structural analysis of cardiomyocytes derived from patient-specific and human ESC-derived stem cell lines lacking ALPK3 revealed disordered sarcomeres and intercalated discs. Multi-electrode array analysis and calcium imaging demonstrated an extended field potential duration and abnormal calcium handling in mutant contractile cultures. CONCLUSIONS: This study validates the genetic evidence, suggesting that mutations in ALPK3 can cause familial cardiomyopathy and demonstrates loss of function as the underlying genetic mechanism. We show that ALPK3-deficient cardiomyocytes derived from pluripotent stem cell models recapitulate the ultrastructural and electrophysiological defects observed in vivo. Analysis of differentiated contractile cultures identified abnormal calcium handling as a potential feature of cardiomyocytes lacking ALPK3, providing functional insights into the molecular mechanisms underlying ALPK3-mediated cardiomyopathy.

Mutations in RAB39B cause X-linked intellectual disability and early-onset Parkinson disease with α-synuclein pathology.

Advances in understanding the etiology of Parkinson disease have been driven by the identification of causative mutations in families. Genetic analysis of an Australian family with three males displaying clinical features of early-onset parkinsonism and intellectual disability identified a ∼45 kb deletion resulting in the complete loss of RAB39B. We subsequently identified a missense mutation (c.503C>A [p.Thr168Lys]) in RAB39B in an unrelated Wisconsin kindred affected by a similar clinical phenotype. In silico and in vitro studies demonstrated that the mutation destabilized the protein, consistent with loss of function. In vitro small-hairpin-RNA-mediated knockdown of Rab39b resulted in a reduction in the density of α-synuclein immunoreactive puncta in dendritic processes of cultured neurons. In addition, in multiple cell models, we demonstrated that knockdown of Rab39b was associated with reduced steady-state levels of α-synuclein. Post mortem studies demonstrated that loss of RAB39B resulted in pathologically confirmed Parkinson disease. There was extensive dopaminergic neuron loss in the substantia nigra and widespread classic Lewy body pathology. Additional pathological features included cortical Lewy bodies, brain iron accumulation, tau immunoreactivity, and axonal spheroids. Overall, we have shown that loss-of-function mutations in RAB39B cause intellectual disability and pathologically confirmed early-onset Parkinson disease. The loss of RAB39B results in dysregulation of α-synuclein homeostasis and a spectrum of neuropathological features that implicate RAB39B in the pathogenesis of Parkinson disease and potentially other neurodegenerative disorders.

Expanding the phenotypic spectrum of ARID1B-mediated disorders and identification of altered cell-cycle dynamics due to ARID1B haploinsufficiency.

BACKGROUND: Mutations in genes encoding components of the Brahma-associated factor (BAF) chromatin remodeling complex have recently been shown to contribute to multiple syndromes characterised by developmental delay and intellectual disability. ARID1B mutations have been identified as the predominant cause of Coffin-Siris syndrome and have also been shown to be a frequent cause of nonsyndromic intellectual disability. Here, we investigate the molecular basis of a patient with an overlapping but distinctive phenotype of intellectual disability, plantar fat pads and facial dysmorphism. METHODS/RESULTS: High density microarray analysis of the patient demonstrated a heterozygous deletion at 6q25.3, which resulted in the loss of four genes including AT Rich Interactive Domain 1B (ARID1B). Subsequent quantitative real-time PCR analysis revealed ARID1B haploinsufficiency in the patient. Analysis of both patient-derived and ARID1B knockdown fibroblasts after serum starvation demonstrated delayed cell cycle re-entry associated with reduced cell number in the S1 phase. Based on the patient's distinctive phenotype, we ascertained four additional patients and identified heterozygous de novo ARID1B frameshift or nonsense mutations in all of them. CONCLUSIONS: This study broadens the spectrum of ARID1B associated phenotypes by describing a distinctive phenotype including plantar fat pads but lacking the hypertrichosis or fifth nail hypoplasia associated with Coffin-Siris syndrome. We present the first direct evidence in patient-derived cells that alterations in cell cycle contribute to the underlying pathogenesis of syndromes associated with ARID1B haploinsufficiency.

Mutations in SH3PXD2B cause Borrone dermato-cardio-skeletal syndrome.

Borrone Dermato-Cardio-Skeletal (BDCS) syndrome is a severe progressive autosomal recessive disorder characterized by coarse facies, thick skin, acne conglobata, dysmorphic facies, vertebral abnormalities and mitral valve prolapse. We identified a consanguineous kindred with a child clinically diagnosed with BDCS. Linkage analysis of this family (BDCS1) identified five regions homozygous by descent with a maximum LOD score of 1.75. Linkage analysis of the family that originally defined BDCS (BDCS3) identified an overlapping linkage peak at chromosome 5q35.1. Sequence analysis identified two different homozygous mutations in BDCS1 and BDCS3, affecting the gene encoding the protein SH3 and PX domains 2B (SH3PXD2B), which localizes to 5q35.1. Western blot analysis of patient fibroblasts derived from affected individuals in both families demonstrated complete loss of SH3PXD2B. Homozygosity mapping and sequence analysis in a second published BDCS family (BDCS2) excluded SH3PXD2B. SH3PXD2B is required for the formation of functional podosomes, and loss-of-function mutations in SH3PXD2B have recently been shown to underlie 7 of 13 families with Frank-Ter Haar syndrome (FTHS). FTHS and BDCS share some overlapping clinical features; therefore, our results demonstrate that a proportion of BDCS and FTHS cases are allelic. Mutations in other gene(s) functioning in podosome formation and regulation are likely to underlie the SH3PXD2B-mutation-negative BDSC/FTHS patients.

ironXS: high-school screening for hereditary haemochromatosis is acceptable and feasible.

As the results of the Human Genome Project are realised, screening for genetic mutations that predispose to preventable disease is becoming increasingly possible. How and where such screening should best be offered are critical, unanswered questions. This study aimed to assess the acceptability and feasibility of genetic screening for preventable disease, using the model of hereditary haemochromatosis, in high-school students. Screening was offered for the HFE C282Y substitution to 17,638 students. Questionnaires were administered at the time of screening (Q1) and approximately 1 month after results were communicated (Q2). Outcomes assessed were uptake of screening, change in scores of validated anxiety, affect and health perception scales from Q1 to Q2, knowledge and iron indices in C282Y homozygous individuals. A total of 5757 (32.6%) students had screening and 28 C282Y-homozygous individuals (1 in 206) were identified, and none of the 27 individuals who had iron indices measures had significant iron overload. There was no significant change in measures of anxiety, affect or health perception in C282Y homozygous or non-homozygous individuals. Over 86% of students answered each of five knowledge questions correctly at Q1. Genetic population-based screening for a preventable disease can be offered in schools in a way that results in minimal morbidity for those identified at high risk of disease. The results of this study are not only relevant for haemochromatosis, but for other genetic markers of preventable disease such as those for cardiovascular disease and cancer.

Deletion of the Parkin co-regulated gene causes defects in ependymal ciliary motility and hydrocephalus in the quakingviable mutant mouse.

The quakingviable mouse (qkv) is a spontaneous recessive mouse mutant with a deletion of approximately 1.1 Mb in the proximal region of chromosome 17. The deletion affects the expression of three genes; quaking (Qk), Parkin-coregulated gene (Pacrg) and parkin (Park2). The resulting phenotype, which includes dysmyelination of the central nervous system and male sterility, is due to reduced expression of Qk and a complete lack of Pacrg expression, respectively. Pacrg is required for correct development of the spermatozoan flagella, a specialized type of motile cilia. In vertebrates, motile cilia are required for multiple functions related to cellular movement or movement of media over a stationary cell surface. To investigate the potential role of PACRG in motile cilia we analysed qkv mutant mice for evidence of cilial dysfunction. Histological and magnetic resonance imaging analyses demonstrated that qkv mutant mice were affected by acquired, communicating hydrocephalus (HC). Structural analysis of ependymal cilia demonstrated that the 9 + 2 arrangement of axonemal microtubules was intact and that both the density of ciliated cells and cilia length was similar to wild-type littermates. Cilia function studies showed a reduction in ependymal cilial beat frequency and cilial mediated flow in qkv mutant mice compared with wild-type littermate controls. Moreover, transgenic expression of Pacrg was necessary and sufficient to correct this deficit and rescue the HC phenotype in the qkv mutant. This study provides novel in vivo evidence that Pacrg is required for motile cilia function and may be involved in the pathogenesis of human ciliopathies, such as HC, asthenospermia and primary ciliary dyskinesia.

Molecular analysis of the PArkin co-regulated gene and association with male infertility.

OBJECTIVE: To investigate the potential role of PArkin co-regulated gene (PACRG) in human male infertility. DESIGN: Case-control study. SETTING: Academic reproductive biology department. PATIENT(S): Blood samples were obtained from 610 patients and 156 normal control subjects. INTERVENTION(S): Genomic DNA was used as template for polymerase chain reaction amplification of the PACRG promoter and coding exons. The amplified fragments were tested for DNA sequence variations by direct sequencing and restriction enzyme analysis. MAIN OUTCOME MEASURE(S): Gene structure and sequence alterations of PACRG in infertile male patients. RESULT(S): The structure of PACRG was determined to comprise 5 coding exons, generating a single transcript in the testis which encoded a predicted protein of 257 amino acids. No pathogenic mutations were identified; however, a variant in the promoter of PACRG was shown to be significantly associated with azoospermia, but not oligospermia, in the case-control cohort. CONCLUSION(S): Mutation of PACRG was not identified as a cause of male infertility, but variation in the promoter was demonstrated to be a risk factor associated with azoospermia.

Expression and localization of the Parkin co-regulated gene in mouse CNS suggests a role in ependymal cilia function.

Parkin Co-Regulated Gene (PACRG) is a gene that shares a bi-directional promoter with the Parkinson's disease associated gene parkin. The functional role of PACRG is not well understood, although the gene has been associated with parkinsonian syndromes and more recently with eukaryotic cilia and flagella. We investigated the expression of Pacrg in the mouse brain by in situ hybridization and observed robust expression of Pacrg in the cells associated with the lateral, third and fourth ventricle, in addition to the aqueduct of Sylvius and choroid plexus. For all regions of Pacrg expression identified, strong expression was observed in the newborn period and this was maintained into adulthood. Immunohistochemical analysis showed that Pacrg was a component of the ependymal cells and cilia lining the ventricles. Based on our results and the previous association of PACRG homologues with cilia and flagella, we propose that Pacrg is a component of the ependymal cilia and may play an important role in motile cilia development and/or function in the CNS.

Regional and cellular localisation of Parkin co-regulated gene in developing and adult mouse brain.

Parkin Co-Regulated Gene (PACRG) is a novel gene that is oriented in a head-to-head array with parkin, and expression of the two genes is regulated by a shared bi-directional promoter. Mutations in parkin are the most common cause of early-onset autosomal recessive Parkinson's disease, however the function of PACRG and potential role in the pathogenesis of Parkinson's disease are unclear. We generated polyclonal anti-PACRG antisera and performed immunohistochemical analysis of the regional and temporal distribution of Pacrg in the mouse brain. The protein was heterogeneously expressed in neurons throughout the mouse brain, with highest levels observed in the rhombencephalon and mesencephalon. Expression was detectable at 1 week of age, increased to maximal levels by 4 weeks and subsequently declined after 3 months. Comparison of parkin and Pacrg immunohistochemistry demonstrated a correlation of both staining distribution and intensity for the two proteins. These results suggest that the transcriptional co-regulation of Pacrg and parkin leads to a similar regional protein distribution in mouse brain, which may have functional significance for the two proteins.

IL-12p40 and IL-18 in crescentic glomerulonephritis: IL-12p40 is the key Th1-defining cytokine chain, whereas IL-18 promotes local inflammation and leukocyte recruitment.

Experimental crescentic glomerulonephritis (GN) is characterized by T helper 1 (Th1) directed nephritogenic immune responses and cell-mediated glomerular injury. IL-12p40, the common cytokine chain for both IL-12 and IL-23, is important in the generation and potentially the maintenance of Th1 responses, whereas IL-18 is a co-factor for Th1 responses that may have systemic and local proinflammatory effects. For testing the hypothesis that both endogenous IL-12p40 and endogenous IL-18 play pathogenetic roles in crescentic GN, accelerated anti-glomerular basement membrane GN was induced in mice genetically deficient in IL-12p40 (IL-12p40-/-), IL-18 (IL-18-/-), or both IL-12p40 and IL-18 (IL-12p40-/-IL-18-/-). Compared with wild-type C57BL/6 mice, IL-12p40-/- mice failed to make a nephritogenic Th1 response and developed markedly reduced crescent formation and renal leukocytic infiltration, despite renal production of chemoattractants and adhesion molecules. IL-18-/- mice developed an intact antigen-specific systemic Th1 response, a similar degree of crescent formation, but fewer glomeruli affected by other severe histologic changes and fewer leukocytes in glomeruli and interstitium. IL-18 was expressed within diseased kidneys. Local production of TNF, IL-1beta, IFN-gamma, CCL3 (MIP-1alpha), and CCL4 (MIP-1beta) was reduced in IL-18-/- mice, demonstrating a local proinflammatory role for IL-18. Combined deletion of IL-12p40 and IL-18 did not result in synergistic effects. Consistent with the hypothesis that inflammation leads to fibrosis, all three groups of deficient mice expressed lower levels of intrarenal TGF-beta1 and/or alpha1(I) procollagen mRNA. These studies demonstrate that in severe experimental crescentic GN, IL-12p40 is the key Th1-defining cytokine chain, whereas IL-18 has local proinflammatory roles.

Experimental autoimmune Goodpasture's disease: a pathogenetic role for both effector cells and antibody in injury.

BACKGROUND: Goodpasture's disease [antiglomerular basement membrane (GBM) glomerulonephritis] is a classic autoimmune disease and the only organ-specific autoimmune renal disease in which the antigen is well described. The importance of antibodies against the non-collagenous domain of the alpha3 chain of type IV collagen [alpha3(IV)NC1] is well established. However, observational human studies and studies in experimental systems also imply a role for cell-mediated effector injury. METHODS: Active experimental autoimmune glomerulonephritis (EAG) was induced by immunization with alpha3-alpha5(IV)NC1 heterodimers in B cell intact C57BL/6 mice and B cell (mu chain-deficient) mice. Passive disease was induced by transferring sera from B cell intact and B cell deficient mice with EAG to RAG-1-/- mice (that lack adaptive immunity). Histologic and functional injury was studied. RESULTS: Despite the absence of B cells and immunoglobulin in B-cell-deficient mice, histologic and functional injury developed in mice immunized with alpha3-alpha5(IV)NC1, with T cells and macrophages in glomeruli. Injury occurred to a similar degree to that found in B-cell-intact mice. Transfer of sera from B-cell-intact mice with EAG containing antibodies (but not from B-cell-deficient mice with EAG) to RAG-1-/- mice induced linear immunoglobulin deposits on the glomerular basement membrane (GBM) and pathologic proteinuria. CONCLUSION: Both cell-mediated and humoral effectors are capable of inducing renal injury in EAG. Given the similarity of the disease-initiating antigen in this model to the antigen in human anti-GBM glomerulonephritis, similar overlapping mechanisms are likely to operate in human disease.

Experimental autoimmune anti-glomerular basement membrane glomerulonephritis: a protective role for IFN-gamma.

IL-12 and IFN-gamma play key roles in murine lupus and planted antigen models of glomerulonephritis. However, their roles in renal organ-specific autoimmunity are unknown. To establish the roles of endogenous IFN-gamma and IL-12 in experimental autoimmune anti-glomerular basement membrane (GBM) glomerulonephritis (EAG), EAG was induced in normal C57BL/6 mice (WT), IL-12p40-deficient (IL-12p40-/-) mice, and IFN-gamma-deficient (IFN-gamma-/-) mice by immunization with alpha3-alpha5(IV)NC1 heterodimers. At 13 wk, WT mice developed EAG with linear mouse anti-GBM antibody deposition, histologic injury, proteinuria, and mild tubulointerstitial disease. Compared with WT mice, IL-12p40-/- mice had decreased histologic injury and trends to decreased leukocyte infiltrates. In contrast, 40% (4 of 10) of IFN-gamma-/- mice developed significant crescent formation and focal or diffuse interstitial infiltrates (WT, 0 of 8). Compared with WT and/or IL-12p40-/- mice, IFN-gamma-/- mice developed increased injury: histologic injury, total glomerular cell numbers, leukocytes in glomeruli, and renal expression of P-selectin and intercellular adhesion molecule 1. All groups developed similar serum anti-alpha3-alpha5(IV)NC1 antibodies and glomerular Ig deposition, but IFN-gamma-/- mice had decreased anti-alpha3-alpha5(IV)NC1 IgG2a. Therefore, IFN-gamma-/- mice developed increased cellular reactants despite a potentially less damaging antibody response. Dermal delayed-type hypersensitivity was increased in alpha3-alpha5(IV)NC1 immunized IFN-gamma-/- mice and was suppressed by recombinant murine IFN-gamma. CD4+ cells from draining nodes of immunized IFN-gamma-/- mice showed increased proportions of proliferating CD4+ cells but similar numbers of apoptotic cells. These studies demonstrate that in renal organ-specific autoimmunity, IL-12 is pathogenetic but IFN-gamma is protective. They lend weight to the hypothesis that depending on the context/severity of the nephritogenic immune response IFN-gamma has different effects.