Neurological autoimmunity targeting aquaporin-4.

Neuromyelitis optica (NMO) is the first inflammatory autoimmune demyelinating disease of the CNS for which a specific tissue target molecule has been identified--the astrocytic water channel aquaporin-4 (AQP4). Immunological insights have propelled significant advances in understanding the clinical, radiologic and immunopathologic characteristics of the disease in the last 5 years. In this review, we describe features distinguishing CNS AQP4 autoimmunity from classical multiple sclerosis (MS). In NMO, disease attacks preferentially involve the optic nerves and spinal cord (hence the name), but neurological signs in the initial attack of AQP4 autoimmunity in children commonly involve the brain. A clinically validated serum biomarker, NMO-IgG, distinguishes relapsing CNS inflammatory demyelinating disorders related to NMO from MS. The NMO-IgG autoantibody is AQP4-specific. Clinical, radiological and immunopathological data support its role in the pathogenesis of NMO spectrum disorders. Lesions characteristic of NMO are distinct from MS: AQP4 and its coupled glutamate transporter, excitatory amino acid transporter 2 (EAAT2), are lost, with and without associated myelin loss, IgG, IgM and complement are deposited in a vasculocentric pattern, edema and inflammation are prominent. In vitro studies demonstrate that binding of NMO-IgG to astrocytic AQP4 initiates multiple potentially neuropathogenic mechanisms: complement activation, AQP4 and EAAT2 downregulation with disruption of water and glutamate homeostasis, enhanced blood-brain barrier permeability, plasma protein and granulocyte influx, and antibody-dependent cell-mediated cytotoxicity. Development of effective, and potentially curative, therapies requires validated models of the disease, in animals and cell culture systems.

Pathogenic potential of IgG binding to water channel extracellular domain in neuromyelitis optica.

BACKGROUND: Autoantibody specific for the aquaporin-4 astrocytic water channel is restricted to serum and CSF of patients with neuromyelitis optica (NMO) and related CNS inflammatory demyelinating disorders (relapsing optic neuritis and longitudinally extensive transverse myelitis). NMO-typical lesions are distinct from MS-typical lesions. Aquaporin-4 is lost selectively at vasculocentric sites of edema/inflammation coinciding with focal deposits of immunoglobulins (Ig) G, M, and terminal complement products, with and without myelin loss. Evidence for antigen-specific autoantibody pathogenicity is lacking. METHODS: We used confocal microscopy and flow cytometry to evaluate the selectivity and immunopathological consequences of Ig binding to surface epitopes of living target cells expressing aquaporin-4 fused at its cytoplasmic N-terminus with GFP. We tested serum, IgG-enriched and IgG-depleted serum fractions, and CSF from patients with NMO, neurologic control patients, and healthy subjects. We also analyzed aquaporin-4 immunoreactivity in myelinated adult mouse optic nerves and spinal cord, and plasma cell Ig isotypes in archived brain tissue from an NMO patient. RESULTS: Serum IgG from patients with NMO binds to the extracellular domain of aquaporin-4; it is predominantly IgG(1), and it initiates two potentially competing outcomes, aquaporin-4 endocytosis/degradation and complement activation. Serum and CSF lack aquaporin-4-specific IgM, and plasma cells in CNS lesions of NMO contain only IgG. Paranodal astrocytic endfeet highly express aquaporin-4. CONCLUSIONS: NMO patients' serum IgG has a selective pathologic effect on cell membranes expressing aquaporin-4. IgG targeting astrocytic processes around nodes of Ranvier could initiate demyelination.

Genetic, functional, and histopathological evaluation of two C-terminal BRCA1 missense variants.

BACKGROUND: The vast majority of BRCA1 missense sequence variants remain uncharacterized for their possible effect on protein expression and function, and therefore are unclassified in terms of their pathogenicity. BRCA1 plays diverse cellular roles and it is unlikely that any single functional assay will accurately reflect the total cellular implications of missense mutations in this gene. OBJECTIVE: To elucidate the effect of two BRCA1 variants, 5236G>C (G1706A) and 5242C>A (A1708E) on BRCA1 function, and to survey the relative usefulness of several assays to direct the characterisation of other unclassified variants in BRCA genes. METHODS AND RESULTS: Data from a range of bioinformatic, genetic, and histopathological analyses, and in vitro functional assays indicated that the 1708E variant was associated with the disruption of different cellular functions of BRCA1. In transient transfection experiments in T47D and 293T cells, the 1708E product was mislocalised to the cytoplasm and induced centrosome amplification in 293T cells. The 1708E variant also failed to transactivate transcription of reporter constructs in mammalian transcriptional transactivation assays. In contrast, the 1706A variant displayed a phenotype comparable to wildtype BRCA1 in these assays. Consistent with functional data, tumours from 1708E carriers showed typical BRCA1 pathology, while tumour material from 1706A carriers displayed few histopathological features associated with BRCA1 related tumours. CONCLUSIONS: A comprehensive range of genetic, bioinformatic, and functional analyses have been combined for the characterisation of BRCA1 unclassified sequence variants. Consistent with the functional analyses, the combined odds of causality calculated for the 1706A variant after multifactorial likelihood analysis (1:142) indicates a definitive classification of this variant as "benign". In contrast, functional assays of the 1708E variant indicate that it is pathogenic, possibly through subcellular mislocalisation. However, the combined odds of 262:1 in favour of causality of this variant does not meet the minimal ratio of 1000:1 for classification as pathogenic, and A1708E remains formally designated as unclassified. Our findings highlight the importance of comprehensive genetic information, together with detailed functional analysis for the definitive categorisation of unclassified sequence variants. This combination of analyses may have direct application to the characterisation of other unclassified variants in BRCA1 and BRCA2.

The involvement of ovarian tumour in the intracellular localization of Sex-lethal protein.

The Drosophila ovarian tumour gene is required at multiple times in the germline for oogenesis. A second gene, Sex-lethal, controls sex determination in the soma and also has a separate germline function affecting similar oogenic stages as ovarian tumour. We demonstrate that ovarian tumour is not required for early Sex-lethal gene expression in the female germline, as had been previously reported. Instead, we provide evidence that ovarian tumour has a specific role in the developmentally regulated accumulation of SEX-LETHAL protein within the cytoplasm and nucleus. Furthermore, the examination of nurse cell polytene chromosomes produced by certain ovarian tumour mutations showed that SEX-LETHAL protein can associate with discrete chromosomal sites in the germline and that this pattern appears to change as the egg chamber matures. This is the first indication that SEX-LETHAL is capable of direct physical interactions with chromosomes (albeit in a mutant background) and is consistent with the developmentally regulated nuclear localization of SEX-LETHAL being important for oogenesis.

Structural analysis of the 17q22-23 amplicon identifies several independent targets of amplification in breast cancer cell lines and tumors.

A novel region of amplification in breast tumors has recently been identified on chromosome 17q22-23. In an effort to identify the oncogenes in the region that are targeted by the amplification process, we determined the structure of the amplicon in breast cancer cell lines and tumors. Physical and transcription maps of the approximately 3.5-Mb region were established and used as the basis for copy number analysis within the region by Southern blot and fluorescence in situ hybridization. Seven specific and independent amplification maxima were identified in breast cancer cell lines and breast tumors. We present correlative amplification and overexpression studies for the FLJ21316 and Hs.6649 genes suggesting a role for these candidates as amplification-dependent oncogenes.

Job satisfaction of Asian Americans.

Since Asian Americans have demographic and labor force characteristics more similar to Euro-Americans than African Americans, one might predict that their job satisfaction would be more like the former than the latter. And, because Asian Americans originating from different countries are heterogeneous in language, culture, and recency of immigration, one might predict that they may report obtaining different amounts of satisfaction from their jobs. However, data from 21 nationally representative opinion surveys from 1972 through 1996 suggest the opposite. Asian Americans (n = 199) reported job satisfaction more like African Americans (n = 1,231) than Euro-Americans (n = 10,709), and Asian Americans from China (n = 53), Japan (n = 44), India (n = 55), and the Philippines (n = 47) reported similar job satisfaction. These differences persisted when age, education, occupation, and personal income were held constant.

Regulatory and functional interactions between ovarian tumor and ovo during Drosophila oogenesis.

The ovo and ovarian tumor genes are required during early and late stages of Drosophila oogenesis. The ovo product, a zinc-finger transcription factor, can bind to sites and influence the level of expression of the ovarian tumor promoter. Our examination of ovo null mutant organelles demonstrate that it is required for the differentiation of XX germ cells during larval gonial stages, in addition to its known role in maintaining germ cell numbers. In contrast, ovarian tumor is required during pupal and adult stages for the cystocyte divisions that give rise to the egg chamber. Studies on sexually transformed flies indicate that both the ovo and ovarian tumor null mutant phenotypes are distinctive from and more severe than the germline defects produced when male germ cells develop in female soma. This suggests that ovo and ovarian tumor have oogenic functions other than their putative role in germline sex determination. We also demonstrate that the regulation of ovarian tumor by ovo is stage-specific, as ovarian tumor promoter activity does not require ovo during larval stages but becomes ovo-dependent in the adult ovary. This coincides with when the ovarian tumor promoter becomes responsive to sex-specific signals from the soma suggesting a convergence of somatic and germline regulatory pathways on ovarian tumor during oogenesis.

Regulatory and functional interactions between the somatic sex regulatory gene transformer and the germline genes ovo and ovarian tumor.

In Drosophila, compatibility between the sexually differentiated state of the soma and the sex chromosome constitution of the germline is required for normal gametogenesis. In this study, we defined important aspects of the soma-germline interactions controlling early oogenesis. In particular, the sex-specific germline activity of the ovarian tumor promoter was found to be dependent upon somatic factors controlled by the somatic sex differentiation gene transformer. This regulation defines whether there is sufficient ovarian tumor expression in adult XX germ cells to support oogenesis. In addition, the ovarian tumor function required for female germline differentiation is dependent on the activity of another germline gene, ovo, whose regulation is transformer-independent. These and other data indicate that ovarian tumor plays a central role in coordinating regulatory inputs from the soma (as regulated by transformer) with those from the germline (involving ovo). We also demonstrate that transformer-dependent interactions influence whether XX germ cells require ovarian tumor or ovo functions to undergo early gametogenic differentiation. These results are incorporated into a model hypothesizing that the functions of ovarian tumor and ovo are dependent on an early sex determination decision in the XX germline that is at least partially controlled by somatic transformer activity.