Dataset Information

Complement Factor H-Related Protein 4A Is the Dominant Circulating Splice Variant of CFHR4.

ABSTRACT: Recent research has elucidated circulating levels of almost all factor H-related (FHR) proteins. Some of these proteins are hypothesized to act as antagonists of the important complement regulator factor H (FH), fine-tuning complement regulation on human surfaces. For the CFHR4 splice variants FHR-4A and FHR-4B, the individual circulating levels are unknown, with only total levels being described. Specific reagents for FHR-4A or FHR-4B are lacking due to the fact that the unique domains in FHR-4A show high sequence similarity with FHR-4B, making it challenging to distinguish them. We developed an assay that specifically measures FHR-4A using novel, well-characterized monoclonal antibodies (mAbs) that target unique domains in FHR-4A only. Using various FHR-4A/FHR-4B-specific mAbs, no FHR-4B was identified in any of the serum samples tested. The results demonstrate that FHR-4A is the dominant splice variant of CFHR4 in the circulation, while casting doubt on the presence of FHR-4B. FHR-4A levels (avg. 2.55?±?1.46?µg/mL) were within the range of most of the previously reported levels for all other FHRs. FHR-4A was found to be highly variable among the population, suggesting a strong genetic regulation. These results shed light on the physiological relevance of the previously proposed role of FHR-4A and FHR-4B as antagonists of FH in the circulation.

SUBMITTER: Pouw RB

PROVIDER: S-EPMC5913293 | biostudies-literature | 2018

REPOSITORIES: biostudies-literature

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Complement Factor H-Related Protein 4A Is the Dominant Circulating Splice Variant of <i>CFHR4</i>.

Pouw Richard B RB Brouwer Mieke C MC van Beek Anna E AE Józsi Mihály M Wouters Diana D Kuijpers Taco W TW

Frontiers in immunology 20180417

Recent research has elucidated circulating levels of almost all factor H-related (FHR) proteins. Some of these proteins are hypothesized to act as antagonists of the important complement regulator factor H (FH), fine-tuning complement regulation on human surfaces. For the <i>CFHR4</i> splice variants FHR-4A and FHR-4B, the individual circulating levels are unknown, with only total levels being described. Specific reagents for FHR-4A or FHR-4B are lacking due to the fact that the unique domains i ...[more]

PMID: 29719534

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Project description:ImportanceThe complement factor H R1210C rare variant confers the strongest genetic risk for age-related macular degeneration and earlier age at onset; however, its associated phenotype has not been well characterized.ObjectiveTo describe specific fundus features of a white population with the R1210C rare variant.Design, setting, and participantsFundus features specific for diagnosis and disease staging were retrospectively characterized by systematic review of all available fundus images for each patient, including color photography, fluorescein angiography, fundus autofluorescence, and optical coherence tomography, at a tertiary ophthalmologic referral center. For this retrospective observational study conducted from 2012 to 2014, enrolled patients with the variant and their family members without the variant were identified from the Age-Related Macular Degeneration Study for a family-based study arm. For patients with the variant but without a family member enrolled in the study, age-matched comparison individuals without the variant were selected randomly from the database.Main outcomes and measuresThe presence of drusen in the macula (macular drusen score) and estimated number (total macular drusen score) were assessed. The presence of drusen in the extramacular regions (extramacular drusen score), pigmentary abnormalities, and disease staging were also evaluated. Binary logistic regression models were used to evaluate the association between rare variant status and ocular phenotypes.ResultsImages from a total of 143 patients (283 eyes), including 62 patients with the rare variant, were analyzed. Drusen score covariates were associated with the R1210C rare variant. A larger proportion of patients carrying the variant had the highest level of macular and total macular drusen scores compared with those without the variant (57.9% vs 16.7% and 52.9% vs 14.2%, respectively; P for trend < .001 for both scores). Patients carrying the rare variant had a much greater likelihood of having advanced disease (odds ratio, 7.0; 95% CI, 3.1-16.2; P < .001). A higher prevalence of geographic atrophy was observed among patients carrying the variant (odds ratio, 13.7; 95% CI, 5.0-37.7; P < .001).Conclusions and relevanceThe typical phenotype of the complement factor H R1210C rare variant is associated with extensive drusen accumulation in the macula and throughout the fundus, as well as with a high risk for having advanced disease. Better characterization of genetic profiles in age-related macular degeneration may be important for screening and future therapeutic strategies for this vision-threatening condition.

Dataset Information

Complement Factor H-Related Protein 4A Is the Dominant Circulating Splice Variant of CFHR4.

Publications

Complement Factor H-Related Protein 4A Is the Dominant Circulating Splice Variant of <i>CFHR4</i>.

Similar Datasets

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