Recent Advances in Genetics of Retinal Dystrophies and Gene Therapy. Anita Agarwal, MD West Coast Retina San Francisco, CA

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1 Recent Advances in Genetics of Retinal Dystrophies and Gene Therapy Anita Agarwal, MD West Coast Retina San Francisco, CA

2 None Disclosures

3 Retinal Dystrophies Able to identify the disease causing gene(s) Explain the biochemical and physiologic mechanism(s) of the defect Understand the structural changes with imaging Treatment of some of the dystrophies Gene therapy replacing defective genes

4 Dystrophies Best s Vitelliform Dystrophy (VMD2 gene) Other VMD2 Gene Defects North Carolina Macular Dystrophy Malattia leventinese Stargardt s disease (Fundus flavimaculatus) Alport s Disease CRB1 mutation (LCA, Coats type RP, PAPRPE-RP)

5 Bests Vitelliform Dystrophy Brilliant Hyper Autofluorescence

6 Best s: Vitelliform space Egg Yolk

7 Best s: Vitelliform space persists

8 Best s: Atypical Multifocal

9 Bestrophin-1 protein localizes to the basolateral plasma membrane of the RPE and Intracellularly Participates in Ca 2+ activated Cl - channel, a Ca 2+ channel regulator, a volume regulated Cl - channel, and a HCO3 - channel.

10 Bestrophin -1 Protein Electro-oculogram (EOG) reflects ion conductance of the RPE light peak (LP) response of EOG is presumed to be generated by activation of a Ca 2+ -sensitive Cl - conductance LP of EOG is reduced in VMD2 gene defective disorders

11 Best Disease (BVMD) More than 100 mutations Mostly Missense mutations at the N- terminal end of the protein Accumulates vitelliform material & fluid in macula Reduced EOG

12 VMD2 gene defect Accumulation of A2E, which originates from photoreceptor visual pigment - Retinal Altered turnover of photoreceptor outer segments Also affects growth & development of eye Hence ADMRCS microphthalmos, cataract, rod cone dystrophy, staphyloma

13 Newer conditions- Best gene Autosomal Dominant Vitreo Retino Choroidopathy (ADVIRC) Autosomal Recessive Bestrophinopathy (ARB) Autosomal Dominant Microcornea, Rod-cone dystrophy, Cataract, Staphyloma (ADMRCS) Adult onset vitelliform maculopathy (Pattern Dystrophy)

14 Autosomal Dominant Vitreo Retino Choroidopathy (ADVIRC)

15 ADVIRC Normal vision No significant nyctalopia Peripheral pigmentary retinopathy Distinct demarcation between normal and abnormal retina 1 st described in family from Chicago

16 Autosomal Recessive Onset ages 4-40 Recessive Bestrophinopathy Multiple Yellow flecks first described in 2008 Increased fundus AF lipofuscin deposition Islands of RPE loss Intraretinal fluid accumulation Courtesy: Dr. Deeksha

17 Courtesy: Camiel Boon ARB Multiple Yellow flecks Increased fundus AF lipofuscin deposition Intraretinal fluid accumulation

18 Autosomal Recessive Bestrophinopathy Homozygous or double heterozygous Null mutation Hence more severe disorder Vitelliform material Intraretinal fluid Narrow angle Microphthalmos

19 North Carolina Macular Dystrophy 2 main phenotypes Drusen & Staphyloma like

20 North Carolina Macular Dystrophy Drusen are compact Distributed in the fovea mostly Radial arrangement of the drusen occ. Asymptomatic Non progressive Unless CNVM

21 2005 Non Progressive Small et al, Hariprasad et al 2009 Daughter & Father

22 NCMD Caldera or Staphyloma phenotype

23 Choroidal cavitation

24 Pathogenesis of ICC in NCMD 30 days: RPE begins to differentiate 6 weeks: Bruch and Choroid begin to form 12 weeks: Sclera forms in posterior pole Development of RPE, Choroid & Sclera highly interdependent Animal models: absence of normal RPE failure of induction of choroid & Sclera

25 Pathogenesis of NCMD Abnormal development of macular RPE in all phenotypes Staphyloma - more severe and earlier in utero ICC: secondary vitreous derived 9 weeks Since developing inner retina is abnormal in NCMD, it is likely vitreous gets trapped within the choroidal defect.

26 NCMD - associated genes Dysregulation of the Retinal Transcription Factor PRDM13 (MCDR1) on Chromosome 6 IRX1 on Chromosome 5 (MCDR3)

27 North Carolina Macular Dystrophy Likely a congenital defect Occurs in-utero Stable, mostly non progressive Original article Kent Small review of original patients

28 Malattia leventinese Doyne s honey comb dystrophy

29 Classic description Nasal drusen EFEMP1 +ve

30 Not always older sister with 20/40 VA EFEMP1 +ve

31 Nodular thickening of the RPE basement membrane/deposition Malattia leventinese

32 Epidermal growth factorcontaining fibulin-like extracellular matrix protein 1 (EFEMP1) Fibulin 3 member of the fibulin family of seven extracellular matrix proteins Accumulation of abnormal ECM material

33 Stargardt s Disease Fundus flavimaculatus Central bull s eye lesion Flecks- pisciform or fish shaped Vermillion fundus Choroidal vessels not visible

34 Stargardt s Disease Dark or silent Choroid Ralph Eagle

35 Stargardt s disease central vision spared until late

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37 Alport s Disease Flecks COL4A5 -Type IV collagen - X linked COL4A3 & COL4A4 Autosomal recessive

38 Alport s Disease - Flecks COL4A5 -Type IV collagen - X linked COL4A3 & COL4A4 Autosomal recessive

39 Flecks of Alport s Disease Thickened / nodular ILM - Flecks Temporal thinning of inner retina

40 Alport s Disease

41 Ghost pockets secondary to thinned out inner retina

42 Alport s Disease Other features described Retinoschisis Macular holes multiple or giant holes Courtesy: David Weinberg

43 AD: Abnormal Type IV collagen Likely affects ILM/Posterior hyaloid interaction - flecks - ILM nodules Likely affects ILM/Posterior hyaloid interaction - secondary Thinning of the inner retina & Ghost pockets Effect on Muller cells & other cells causing thinning of the inner retina

44 CRB1(Crumbs homolog 1) Leber s congenital amaurosis Para arterial preserved RPE Retinitis pigmentosa Coats type RP

45 LCA CRB1 mutation 6 months 11 years

46 Very early onset, nystagmus

47 Thick retina, abnormal lamination

48 Para Arterial Preserved RPE RP

49 Para Arterial Preserved RPE RP

50 Thickened retina

51 Abnormal lamination loss of ELM

52 CRB1 gene product Protein involved at the junction between photoreceptors and Muller cells at the outer limiting membrane Abnormality: zonula adherens

53 CRB1 gene products integral for maintenance of zonula adherens Both LCA and PAPRPE RP show similar retinal architecture Thickened retina Abnormal lamination Absence of ELM Thin Ganglion cell layer

54 16 Year old girl: 2011 Strabismus at age 2 Given glasses Medical Hx: healthy Family Hx; Older sister and parents with no similar issues, no other affected close family members VA: 20/50 & 20/40 (Best corrected) IOP: 13 & 17 Anterior segment: normal OU

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57 Coats type RP

58 Thick retina on OCT

59 Coats type RP Early onset Pigmentary retinopathy Nummular pigment lesions Disc drusen Dilated vessels inferiorly Hyperopia

60 Representative Diagram of Genetic heterogeneity

61 Genetic Diagnostics Array-based primer extension (APEX) tech Sanger sequencing Yield 10-20% Next generation sequencing (NGS) Genomic engineering Chromosome microarrays,

62 APEX technology Detect multiple variants in multiple genes simultaneously But only detects a fixed number of mutations from a fixed number of genes.

63 Next Generation Sequencing (NGS) Massively Parallel sequencing (MPS) sequencing of targeted exonic regions, whole exomes & whole genomes fast and relatively cheaper simultaneously sequence regions in parallel allows for hundreds or thousands of sequencing fragments or reads to cover a single region.

64 Whole Exome Sequencing (WES) Whole Genome Sequencing (WGS) all genes are captured bioinformatic filter can be modified to include examination of novel disease genes. capacity in identification of copy number and structural variants

65 Animal models in rodents & larger animals Knock out models Over expression Gene editing techniques

66 Gene Therapy Monogenic Diseases Delivery of functional cdna to the retina via adeno-associated virus (AAV) vectors LCA- RPE 65 Usher type IB Choroideremia Stargardt s disease Leber s Herditary Optic Neuropathy Achromatopsia

67 RPE65 RPE65 gene replacement therapy SPK- RPE65 AAV2-hRPE65v2 Spark Therapeutics University college of London University of Pennsylvania Applied Genetic Technologies Corp

68 Leber hereditary optic neuropathy ND4 gene replacement therapy scaav2- P1ND4v2 - Univ. of Miami Choroideremia Stargardt s Disease Achromatopsia X linked retinoschisis

69 Stem cells Embryonic stem cells (ESCs), Induced pluripotent stem cells (ipscs) derived from child or adult fibroblast Retinal progenitor cells (RPCs) -

70 Clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9 precise genomic regions can be targeted through easily synthesized guide RNA Edits the genome through inducing double stranded or single stranded breaks Precise Medicine use of CRISPR technique on patient s stem cells to precisely modify (edit) the DNA and re implant

71 Stargardt s Disease Pharmacological approach Fenretinide (N-(4-hydroxyphenyl)retinamide, 4-HPR, Sirion Therapeutics) is a synthetic derivative of vitamin A that competes with vitamin A (retinol) in the eye for binding to retinal binding protein (RBP). A1120

72 Retinal Implants Argus II IRIS II (Europe)

73 Argus II Update Second Sight Argus II Retinal Prosthesis System courtesy: Mark Humayun, MD Camera Transmitter Coil Video Processing Unit (VPU) External video processing unit and glasses Provides significant user control over image processing Upgradable camera, processor, and software System performance not affected by ocular opacity

74 Argus II Update Second Sight Argus II Retinal Prosthesis Retinal tack Dimensions: Equivalent to visual field of 20 Each electrode individually programmable Epiretinal placement using standard vitreoretinal surgical techniques No routine use of silicone oil Surgery can be completed in as little as 2 hours (initially 3 hours) Electrode Array

75 How Does Argus II Work?

76 Summary Imaging & Genetics In Retinal Dystrophies Imaging findings combined with new genetic information Helping understand Pathogenesis & Pathology in some Spearheading genetic & other therapies Still many unanswered questions & findings