Quantification of FAM20A in human milk and identification of calcium metabolism proteins. Issue 24 (27th December 2021)

• Record Type: Journal Article
• Authors: Patel, Vaksha; Klootwijk, Enriko; Whiting, Gail; Bockenhauer, Detlef; Siew, Keith; Walsh, Stephen; Bleich, Markus; Himmerkus, Nina; Jaureguiberry, Graciana; Issler, Naomi; Godovac‐Zimmermann, Jasminka; Kleta, Robert; Wheeler, Jun
• Is Part Of: Physiological reports. Volume 9:Issue 24(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-12-27
• Subjects: calcium metabolism -- enamel renal syndrome -- FAM20A and human milk; Physiology -- Periodicals; 571
• DOI: 10.14814/phy2.15150
• Languages: English
• ISSNs: 2051-817X

Abstract

Abstract: Background: FAM20A, a recently discovered protein, is thought to have a fundamental role in inhibiting ectopic calcification. Several studies have demonstrated that variants of FAM20A are causative for the rare autosomal recessive disorder, enamel‐renal syndrome (ERS). ERS is characterized by defective mineralization of dental enamel and nephrocalcinosis suggesting that FAM20A is an extracellular matrix protein, dysfunction of which causes calcification of the secretory epithelial tissues. FAM20A is a low‐abundant protein that is difficult to detect in biofluids such as blood, saliva, and urine. Thus, we speculated the abundance of FAM20A to be high in human milk, since the secretory epithelium of lactating mammary tissue is involved in the secretion of highly concentrated calcium. Therefore, the primary aim of this research is to describe the processes/methodology taken to quantify FAM20A in human milk and identify other proteins involved in calcium metabolism. Method: This study used mass spectrometry‐driven quantitative proteomics: (1) to quantify FAM20A in human milk of three women and (2) to identify proteins associated with calcium regulation by bioinformatic analyses on whole and milk fat globule membrane fractions. Results: Shotgun MS/MS driven proteomics identified FAM20A in whole milk, and subsequent analysis using targeted proteomics also successfully quantified FAM20A in all samples. Combination of sample preparation, fractionation, and LC‐MS/MS proteomics analysis generated 136 proteins previously undiscovered in human milk; 21 of these appear to be associated with calcium metabolism. Conclusion: Using mass spectrometry‐driven proteomics, we successfully quantified FAM20A from transitional to mature milk and obtained a list of proteins involved in calcium metabolism. Furthermore, we show the value of using a combination of both shotgun and targeted driven proteomics for the identification of this low abundant protein in human milk. Abstract : Variants of FAM20A causes enamel‐renal syndrome which is characterized by defective mineralization of dental enamel and nephrocalcinosis. FAM20A is associated in inhibiting calcification. The article describes the process undertaken to quantify this low abundant protein in human milk and using bioinformatical analysis, have identified potential candidate proteins that could be involved in calcium metabolism and could possibly network with FAM20A.