Loss-of-function mutations in the CFH gene affecting alternatively encoded Factor H-like 1 protein cause dominant early-onset macular drusenCitation formats

  • External authors:
  • James Poulter
  • Susan Downes
  • Martin McKibbin
  • Kamron N. Khan
  • Chris F Inglehearn
  • Andrew R. Webster
  • Alison J Hardcastle
  • Michel Michaelides

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Loss-of-function mutations in the CFH gene affecting alternatively encoded Factor H-like 1 protein cause dominant early-onset macular drusen. / Taylor, Rachel L; Poulter, James; Downes, Susan; McKibbin, Martin; Khan, Kamron N.; Inglehearn, Chris F; Webster, Andrew R.; Hardcastle, Alison J; Michaelides, Michel; Bishop, Paul; Clark, Simon; Black, Graeme.

In: Ophthalmology, 2019.

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Taylor, Rachel L ; Poulter, James ; Downes, Susan ; McKibbin, Martin ; Khan, Kamron N. ; Inglehearn, Chris F ; Webster, Andrew R. ; Hardcastle, Alison J ; Michaelides, Michel ; Bishop, Paul ; Clark, Simon ; Black, Graeme. / Loss-of-function mutations in the CFH gene affecting alternatively encoded Factor H-like 1 protein cause dominant early-onset macular drusen. In: Ophthalmology. 2019.

Bibtex

@article{6f811cd8f3c1475db9a6e1969a892224,
title = "Loss-of-function mutations in the CFH gene affecting alternatively encoded Factor H-like 1 protein cause dominant early-onset macular drusen",
abstract = "Purpose: To characterise the molecular mechanism underpinning early-onset macular drusen (EOMD), a phenotypically severe sub-type of age-related macular degeneration (AMD), in a sub-group of patients. Design: Multi-centre case series, in vitro experimentation and retrospective analysis of previously reported variants. Participants: Seven families with apparently autosomal dominant EOMD. Methods: Patients underwent comprehensive ophthalmic assessment. Affected individuals from families A, B and E underwent whole exome sequencing. The probands from families C, D, F and G underwent Sanger sequencing analysis of the Complement Factor H (CFH) gene. Mutant recombinant Factor H Like-1 (FHL-1) proteins were expressed in HEK293 cells to assess the impact on FHL-1 expression and function. Previously reported EOMD-causing variants in CFH were reviewed. Main Outcome Measures: Detailed clinical phenotypes, genomic findings, in vitro characterization of mutation effect on protein function, and postulation of the pathomechanism underpinning EOMD. Results: All affected participants presented with bilateral drusen. The earliest reported age of onset was 16 years with a median of 46 years). Ultra-rare (MAF ≤0.0001) CFH variants were identified as the cause of disease in each family: CFH c.1243del, p.(Ala415ProfsTer39) het; c.350+1G>T het; c.619+1G>A het, c.380G>A, p.(Arg127His) het; c.694C>T p.(Arg232Ter)het [identified in two unrelated families in this cohort]; and c.1291T>A, p.(Cys431Ser). All mutations affect complement control protein domains (CCP) 2-7, thus are predicted to impact both FHL-1, the predominant isoform in Bruch’s membrane(BrM) of the macula, and FH. In vitro analysis of recombinant proteins FHL-1R127H, FHL-1A415f/s and FHL-1C431S demonstrated that they are not secreted and thus are loss-of-function. Intra-cellular expression of mutant proteins was low, suggesting they may be rapidly degraded due to protein unfolding or instability. Review of 29 previously reported EOMD-causing mutations found that 75.8{\%} (22/29) of impact FHL-1 and FH. In total, 86.2{\%} (25/29) EOMD-associated variants cause haploinsufficiency of FH/FHL-1. Conclusions: EOMD is an under-recognised, phenotypically severe sub-type of AMD. We propose that haploinsufficiency of FHL-1, the main regulator of the complement pathway in BrM, where drusen develop, is an important mechanism underpinning the development of EOMD in a number of cases. Understanding the molecular basis of EOMD will shed light on AMD pathogenesis given their pathological similarities.",
keywords = "early onset macular drusen, age-related macular degeneration, complement factor-H, CFH, FHL-1",
author = "Taylor, {Rachel L} and James Poulter and Susan Downes and Martin McKibbin and Khan, {Kamron N.} and Inglehearn, {Chris F} and Webster, {Andrew R.} and Hardcastle, {Alison J} and Michel Michaelides and Paul Bishop and Simon Clark and Graeme Black",
year = "2019",
doi = "10.1016/j.ophtha.2019.03.013",
language = "English",
journal = "Ophthalmology|Ophthalmology",
issn = "1549-4713",
publisher = "Elsevier BV",

}

RIS

TY - JOUR

T1 - Loss-of-function mutations in the CFH gene affecting alternatively encoded Factor H-like 1 protein cause dominant early-onset macular drusen

AU - Taylor, Rachel L

AU - Poulter, James

AU - Downes, Susan

AU - McKibbin, Martin

AU - Khan, Kamron N.

AU - Inglehearn, Chris F

AU - Webster, Andrew R.

AU - Hardcastle, Alison J

AU - Michaelides, Michel

AU - Bishop, Paul

AU - Clark, Simon

AU - Black, Graeme

PY - 2019

Y1 - 2019

N2 - Purpose: To characterise the molecular mechanism underpinning early-onset macular drusen (EOMD), a phenotypically severe sub-type of age-related macular degeneration (AMD), in a sub-group of patients. Design: Multi-centre case series, in vitro experimentation and retrospective analysis of previously reported variants. Participants: Seven families with apparently autosomal dominant EOMD. Methods: Patients underwent comprehensive ophthalmic assessment. Affected individuals from families A, B and E underwent whole exome sequencing. The probands from families C, D, F and G underwent Sanger sequencing analysis of the Complement Factor H (CFH) gene. Mutant recombinant Factor H Like-1 (FHL-1) proteins were expressed in HEK293 cells to assess the impact on FHL-1 expression and function. Previously reported EOMD-causing variants in CFH were reviewed. Main Outcome Measures: Detailed clinical phenotypes, genomic findings, in vitro characterization of mutation effect on protein function, and postulation of the pathomechanism underpinning EOMD. Results: All affected participants presented with bilateral drusen. The earliest reported age of onset was 16 years with a median of 46 years). Ultra-rare (MAF ≤0.0001) CFH variants were identified as the cause of disease in each family: CFH c.1243del, p.(Ala415ProfsTer39) het; c.350+1G>T het; c.619+1G>A het, c.380G>A, p.(Arg127His) het; c.694C>T p.(Arg232Ter)het [identified in two unrelated families in this cohort]; and c.1291T>A, p.(Cys431Ser). All mutations affect complement control protein domains (CCP) 2-7, thus are predicted to impact both FHL-1, the predominant isoform in Bruch’s membrane(BrM) of the macula, and FH. In vitro analysis of recombinant proteins FHL-1R127H, FHL-1A415f/s and FHL-1C431S demonstrated that they are not secreted and thus are loss-of-function. Intra-cellular expression of mutant proteins was low, suggesting they may be rapidly degraded due to protein unfolding or instability. Review of 29 previously reported EOMD-causing mutations found that 75.8% (22/29) of impact FHL-1 and FH. In total, 86.2% (25/29) EOMD-associated variants cause haploinsufficiency of FH/FHL-1. Conclusions: EOMD is an under-recognised, phenotypically severe sub-type of AMD. We propose that haploinsufficiency of FHL-1, the main regulator of the complement pathway in BrM, where drusen develop, is an important mechanism underpinning the development of EOMD in a number of cases. Understanding the molecular basis of EOMD will shed light on AMD pathogenesis given their pathological similarities.

AB - Purpose: To characterise the molecular mechanism underpinning early-onset macular drusen (EOMD), a phenotypically severe sub-type of age-related macular degeneration (AMD), in a sub-group of patients. Design: Multi-centre case series, in vitro experimentation and retrospective analysis of previously reported variants. Participants: Seven families with apparently autosomal dominant EOMD. Methods: Patients underwent comprehensive ophthalmic assessment. Affected individuals from families A, B and E underwent whole exome sequencing. The probands from families C, D, F and G underwent Sanger sequencing analysis of the Complement Factor H (CFH) gene. Mutant recombinant Factor H Like-1 (FHL-1) proteins were expressed in HEK293 cells to assess the impact on FHL-1 expression and function. Previously reported EOMD-causing variants in CFH were reviewed. Main Outcome Measures: Detailed clinical phenotypes, genomic findings, in vitro characterization of mutation effect on protein function, and postulation of the pathomechanism underpinning EOMD. Results: All affected participants presented with bilateral drusen. The earliest reported age of onset was 16 years with a median of 46 years). Ultra-rare (MAF ≤0.0001) CFH variants were identified as the cause of disease in each family: CFH c.1243del, p.(Ala415ProfsTer39) het; c.350+1G>T het; c.619+1G>A het, c.380G>A, p.(Arg127His) het; c.694C>T p.(Arg232Ter)het [identified in two unrelated families in this cohort]; and c.1291T>A, p.(Cys431Ser). All mutations affect complement control protein domains (CCP) 2-7, thus are predicted to impact both FHL-1, the predominant isoform in Bruch’s membrane(BrM) of the macula, and FH. In vitro analysis of recombinant proteins FHL-1R127H, FHL-1A415f/s and FHL-1C431S demonstrated that they are not secreted and thus are loss-of-function. Intra-cellular expression of mutant proteins was low, suggesting they may be rapidly degraded due to protein unfolding or instability. Review of 29 previously reported EOMD-causing mutations found that 75.8% (22/29) of impact FHL-1 and FH. In total, 86.2% (25/29) EOMD-associated variants cause haploinsufficiency of FH/FHL-1. Conclusions: EOMD is an under-recognised, phenotypically severe sub-type of AMD. We propose that haploinsufficiency of FHL-1, the main regulator of the complement pathway in BrM, where drusen develop, is an important mechanism underpinning the development of EOMD in a number of cases. Understanding the molecular basis of EOMD will shed light on AMD pathogenesis given their pathological similarities.

KW - early onset macular drusen

KW - age-related macular degeneration

KW - complement factor-H

KW - CFH

KW - FHL-1

U2 - 10.1016/j.ophtha.2019.03.013

DO - 10.1016/j.ophtha.2019.03.013

M3 - Article

JO - Ophthalmology|Ophthalmology

JF - Ophthalmology|Ophthalmology

SN - 1549-4713

ER -