S-antigen in non ocular tissues

Epigenome-Wide DNA Methylation in Unipolar Depression: Predictive Biomarker of Antidepressant Treatment Response?

BACKGROUND

Despite the well-documented efficacy of antidepressant agents for the treatment of major depressive disorder (MDD), initial treatment nonresponse rates are high. Recent years have seen an increase in research into predictive biomarkers toward improving diagnosis and individualized treatment. Among those, epigenetic mechanisms such as DNA methylation constitute promising candidate markers in predicting antidepressant treatment response in MDD. The present study sought to address epigenome-wide DNA methylation as a predictor of antidepressant treatment response in the largest sample to date of patients with MDD.

METHODS

Epigenome-wide DNA methylation was analyzed using the Infinium MethylationEPIC BeadChip in peripheral blood of n = 230 Caucasian patients with MDD receiving 6-week antidepressant treatment in a naturalistic in-patient setting as well as in a subsample of n = 107 patients primarily receiving continuous treatment with serotonin reuptake inhibitors or serotonin and norepinephrine reuptake inhibitors. Treatment response was assessed by means of the Hamilton Depression Scale.

RESULTS

No genome-wide significant hits were observed. Suggestive (P < 1E-5) epigenome-wide evidence was discerned for altered DNA methylation at 6 CpG sites (LOC102724467, LOC100506023, RSPO2, SAG, IL16, PRKCI) to predict response to naturalistic antidepressant treatment. In patients treated with serotonin reuptake inhibitors or serotonin and norepinephrine reuptake inhibitors, differential DNA methylation at 11 CpGs, for example, mapping to the TIMP2, VDAC1, or SORL1 genes, was suggestively associated with treatment response.

CONCLUSIONS

The present results provide preliminary evidence for altered DNA methylation patterns to be associated with antidepressant treatment response in MDD. Provided significant replication in independent and larger samples, the present findings might in the future aid in clinical decision-making toward more individualized and thus more efficacious treatments of MDD.

Unilateral paraneoplastic optic disc edema and retinal periphlebitis in pineal germinoma

Purpose

To describe a unilateral ocular paraneoplastic syndrome in pineal germinoma.

Observations

A 24-year-old male presented with diplopia, excessive thirst, and frequent urination. Cranial MRI showed a mass in pineal gland. Dorsal midbrain syndrome signs were present. Examination showed optic disc edema and segmental retinal periphlebitis in right and normal fundus in left eye. Rheumatologic work-up was negative. Brain biopsy confirmed pineal germinoma. Retinal findings were attributed to paraneoplastic syndrome. Resolution of optic disc edema and retinal periphlebitis occurred following chemotherapy and focal irradiation.

Conclusions

and importance: To date there are two published case reports on bilateral optic disc edema and retinal periphlebitis occurring as a paraneoplastic syndrome in pineal germinoma. This is the first report on a patient with pineal germinoma who had unilateral paraneoplastic involvement characterized by optic disc edema and retinal periphlebitis and who showed complete resolution of ocular disease after treatment of underlying tumor.

Isolation and characterization of the human X-arrestin gene

Arrestins are signal transduction modulators that quench the activated state of receptors. X-arrestin (ARRX) is specifically expressed in the red-, green-, and blue-sensitive cone photoreceptors, and is most likely a modulator of cone phototransduction. The human gene for X-arrestin at Xcen-Xq22 has been shown to be approximately 20kb in size and to consist of 17 exons and 16 introns. The exons are generally small, including exon 16 of 10bp, and are clustered into three groups, separated by the two largest introns. This gene structure is generally similar to that of S-antigen, the rod photoreceptor arrestin. There is remarkable similarity, however, among the individual exons between the two genes in that 10 of the exons are identical in size. The 5' upstream region of the X-arrestin gene contains TATA and CAAT boxes, typical of genes expressed in a tissue-specific manner, in contrast to the S-antigen gene, which lacks these promoter sequences. The promoter elements, common to both the X-arrestin and S-antigen genes, include the Ret-1/PCE-1 (PCE-1-like in X-arrestin), CRX, and the thyroid hormone/retinoic acid-responsive sequences, the former two being present in a number of photoreceptor-expressed genes. Three CRX-binding elements, 15bp apart, are present in a cluster. The common promoter elements between the cone-expressed genes, X-arrestin and color opsins, include the TATA box, PCE-1, and CRX-binding sequences, the combination of which might be important for directing cone-specific expression.

Immune privilege in the retina

As new Ag-specific and non-Ag-specific mechanisms contributing to ocular immune privilege are revealed, the relevance of old paradigms properly comes into question. My lab has a particular interest in the immune privilege of the retina. While the presence of active mechanisms of tolerance, such as immune deviation, is now well-established, we propose that sequestration provides the first line of immune privilege in the retina. When it fails, active, inducible mechanisms provide backup to protect the integrity of the retina and vision. Some of the observations that led to our hypotheses and their supporting experiments are discussed below.

S-antigen immunoreactivity in tumors of the choroid plexus

Using monoclonal antibodies (MAbs) directed against retinal S-antigen, the authors demonstrated the presence of S-antigen immunoreactivity in six of six (100%) tumors of the human choroid plexus, a tissue rich in β-adrenergic receptor activity. An anti-retinal S-antigen MAb F4C1, showed S-antigen immunoreactivity in one papilloma of the choroid plexus and in five of five (100%) carcinomas of the choroid plexus. In contrast, a papillary ependymoma of the spinal cord, an astrocytoma, an oligodendroglioma, metastatic oat cell carcinoma and metastatic adenocarcinoma to the brain did not stain. Our study indicates that MAb F4C1 may prove to be a useful immunohistochemical marker of tumors originating from the choroid plexus.

X-arrestin: a new retinal arrestin mapping to the X chromosome

We have been using a differential cDNA cloning approach to isolate human retina-specific and retina-enriched genes [1]. A 1,314 bp cDNA was isolated by this approach, representing a highly retina-specific message encoding a 388 amino acid protein showing 58%, 50%, and 49% homology to bovine beta-arrestin, and bovine and human retinal arrestin (S-antigen), respectively. Chromosomal mapping localized this new arrestin gene to the proximal long arm of the X chromosome, hence it was named X-arrestin. In situ hybridization demonstrated its expression in the inner and outer segments and the inner plexiform regions of the retina.

Enhancement of S-antigen and its mRNA in the irides of uveitic patients

S-antigen (S-Ag) and its mRNA were analysed by immunohistochemistry and in situ hybridization in 32 iridectomy specimens from 29 uveitic patients and 10 non-uveitic patients. S-Ag was detected in one iris and its mRNA was detected in 12 uveitic patients. Neither S-Ag nor its mRNA was found in the controls (P < 0.003). Ten of the 12 patients who had detectable S-Ag mRNA, while only four of the 17 patients who did not, had received corticosteroids for more than 3 years (P = 0.006). We also demonstrated S-Ag and its mRNA in bovine iris by immunoprecipitation and polymerase chain reaction. These results indicate that S-Ag and its mRNA accumulate in the irides of some uveitic patients. This accumulation may be the result of local immunoregulatory factors and an effect of corticosteroid treatment, and may modulate ocular inflammation.

Identification of an S-antigen-like molecule in human choroid plexus and cerebrospinal fluid

Sensitisation to retinal S-antigen has been implicated in the pathogenesis of several clinical forms of posterior uveitis. S-antigen-like molecules have recently been demonstrated in the brain and choroid plexus of experimental animals. We used a panel of four monoclonal antibodies (MAbs), MAbF4-C1, MAbC10-C10, MAbA2-G5 and MAbA9-C6, which define specific epitopes in the amino, mid and carboxyl terminal portions of S-antigen in order to identify an S-antigen-like molecule in human choroid plexus and cerebrospinal fluid (CSF). Three MAbs, MAbF4-C1, MAbC10-C10 and MAbA9-C6, localised an S-antigen-like molecule to the cytoplasm of the epithelial cells of the human choroid plexus. Polymerase chain reaction of cDNA from choroid plexus verified the presence of S-antigen homologues in the choroid plexus. The presence of an S-antigen-like molecule in the CSF was demonstrated by western blots in seven CSF samples from patients with a variety of neuropathological disorders. It is proposed that immunological cross-reactivity and biochemical similarity between retinal S-antigen and an S-antigen-like molecule in human choroid plexus and CSF could form a basis for neurological manifestations observed in certain clinical forms of uveitides.

Developmental expression of S-antigen in fetal human and rat eye

Development expression of S-antigen and its mRNA in human and rat fetal retina was studied by immunocytochemical and in situ hybridization techniques. Immunocytochemistry indicated that S-antigen was present after 4 months gestation in the fetal human retina. In the rat, S-antigen was detected in the retina only after birth. In situ hybridization studies indicated that the S-antigen mRNA was present at 13 weeks gestational age in the human and at 15 days in the rat embryo. S-antigen mRNA was expressed not only in the retina but also in ocular tissues of neural crest origin in the fetus.

Identification of an S-antigen-like molecule in Drosophila melanogaster: an immunohistochemical study

Vision is a highly complex process common to many vertebrate and invertebrate species. The visual system of Drosophila represents a valuable model in which to study this process since its chromosomal makeup has been well mapped and many mutants containing specific photoreceptor defects have been described. S-antigen is a well-characterized photoreceptor cell protein which plays a fundamental role in the visual process. In this study, we used a panel of four monoclonal antibodies (MAbs) specific for amino, mid and carboxy terminal amino acid sequences in S-antigen in order to examine S-antigen immunoreactivity in the Drosophila visual system. Two MAbs, MAb5C6.47 and MAbC10-C10, localized S-antigen to the retinules and ocelli. In contrast, MAbA2-G5 and MAbA9-C6 did not stain. The presence and strong antigenic similarity of an S-antigen homolog in Drosophila suggests that in both vertebrates and invertebrates S-antigen plays a major role in the regulation of the phototransduction of vision.