Scientists from the Duke Medical Center (North Carolina, USA) and the Bascom Palmer Eye Institute at the University of Miami (Florida, USA) have performed liquid chromatography coupled to mass spectrometry (LC?MS) to identify a new diagnostic marker of Retinitis pigmentosa (RP) in patient urine samples.1 RP is a disease of the eye that causes retina degradation and can result in blindness. Often inherited, it has multiple contributing genetic mutations and there is no treatment available.
Scientists from the Duke Medical Center (North Carolina, USA) and the Bascom Palmer Eye Institute at the University of Miami (Florida, USA) have performed liquid chromatography coupled to mass spectrometry (LC–MS) to identify a new diagnostic marker of Retinitis pigmentosa (RP) in patient urine samples.1 RP is a disease of the eye that causes retina degradation and can result in blindness. Often inherited, it has multiple contributing genetic mutations and there is no treatment available.
Ziqiang Guan of Duke Medical University told The Column that his collaborators Rong Wen and Dr Byron Lam at the Bascom Palmer Eye Institute in Miami first discovered that a mutation in the dehydrodolichol diphosphate synthase (DHDDS) gene was responsible for a subtype of RP in 2011. Guan said: “Later, it was found that DHDDS mutations are far more common in individuals of Ashkenazi Jewish heritage than in the general population. My collaborators initially sought my expertise in mass spectrometry (MS) and dolichol analysis to assess the effects of this DHDDS gene mutation on the biosynthesis of dolichol, a lipid with many biological and physiological roles.“
The team began by analyzing cultured cells, fibroblasts, taken from a family in which three out of four children were diagnosed in their teenage years. Reversed-phase LC coupled with multiple-reaction monitoring mode (MRM) was later performed on a triple quadruple mass spectrometer to analyze plasma, and subsequently urine samples. The method was reported by Guan to be very sensitive and require less than 1 mL of urine or blood sample. Furthermore, the ratio meaurement of dolichol-18 and dolichol-19 (D18/D19) for this diagnostic test is a major advantage according to Guan, because it removes the effects of fluctutations in diachols caused by possible changes in diet, fluid intake, and time of collection.
In three siblings diagnosed with RP, dolichol profiles were shorter than in an unaffected sibling from the same family. Dolichol-18 was identified to be at higher or dominating levels in the urine of the affected siblings while dolichol-19 was dominant in the unaffected sibling. When asked to comment on the results, Guan told The Column: ”We were pleasantly surprised that the urinary and plasma dolichol profiles of RP patients could be easily distinguished from those of the carriers, which in turn are different from those of normal individuals. These observations have been verified in a total of nine patients and 35 carriers for whom we have performed dolichol profiling so far.”
The new screening method provides yet another example of how chromatography is making its way into clinical diagnosis. The potential of screening urine and plasma samples for diagnosing genetic disease is a major advantage over existing methods. According to Guan, dolichol profiling is better than gentotyping (analyzing DNA) because it can directly correlate phenotype (disease symptoms) with alterations in metabolism. He said: ”Dolichol profiling can serve as a guide for the future development of therapeutics for RP caused by DHDDS mutations.”- B.D.
Reference
R. Wen, B.L. Lam, and Z. Guan, Journal of Lipid Research DOI: 10.1194/jlr.M043232 (2013).
This story originally appeared in The Column. Click here to view that issue.
The Next Frontier for Mass Spectrometry: Maximizing Ion Utilization
January 20th 2025In this podcast, Daniel DeBord, CTO of MOBILion Systems, describes a new high resolution mass spectrometry approach that promises to increase speed and sensitivity in omics applications. MOBILion recently introduced the PAMAF mode of operation, which stands for parallel accumulation with mobility aligned fragmentation. It substantially increases the fraction of ions used for mass spectrometry analysis by replacing the functionality of the quadrupole with high resolution ion mobility. Listen to learn more about this exciting new development.
The Complexity of Oligonucleotide Separations
January 9th 2025Peter Pellegrinelli, Applications Specialist at Advanced Materials Technology (AMT) explains the complexity of oligonucleotide separations due to the unique chemical properties of these molecules. Issues such as varying length, sequence complexity, and hydrophilic-hydrophobic characteristics make efficient separations difficult. Separation scientists are addressing these challenges by modifying mobile phase compositions, using varying ion-pairing reagents, and exploring alternative separation modes like HILIC and ion-exchange chromatography. Due to these complexities, AMT has introduced the HALO® OLIGO column, which offers high-resolution, fast separations through its innovative Fused-Core® technology and high pH stability. Alongside explaining the new column, Peter looks to the future of these separations and what is next to come.
Evaluating Dissolved Organic Matter with GPC and Spectroscopy
February 4th 2025Gel permeation chromatography, three-dimensional excitation-emission matrix fluorescence spectroscopy, and UV-visible spectroscopy was utilized to assess road runoff passed through a filter filled with sludge from drinking water treatment plants to evaluate its capacity for removing dissolved organic matter (DOM).