Ingele Casteels

Long-term effect of gene therapy on Leber's congenital amaurosis.

BACKGROUND Mutations in RPE65 cause Lebers congenital amaurosis, a progressive retinal degenerative disease that severely impairs sight in children. Gene therapy can result in modest improvements in night vision, but knowledge of its efficacy in humans is limited. METHODS We performed a phase 1-2 open-label trial involving 12 participants to evaluate the safety and efficacy of gene therapy with a recombinant adeno-associated virus 2/2 (rAAV2/2) vector carrying the RPE65 complementary DNA, and measured visual function over the course of 3 years. Four participants were administered a lower dose of the vector, and 8 were administered a higher dose. In a parallel study in dogs, we investigated the relationship among vector dose, visual function, and electroretinography (ERG) findings. RESULTS Improvements in retinal sensitivity were evident, to varying extents, in six participants for up to 3 years, peaking at 6 to 12 months after treatment and then declining. No associated improvement in retinal function was detected by means of ERG. Three participants had intraocular inflammation, and two had clinically significant deterioration of visual acuity. The reduction in central retinal thickness varied among participants. In dogs, RPE65 gene therapy with the same vector at lower doses improved vision-guided behavior, but only higher doses resulted in improvements in retinal function that were detectable with the use of ERG. CONCLUSIONS Gene therapy with rAAV2/2 RPE65 vector improved retinal sensitivity, albeit modestly and temporarily. Comparison with the results obtained in the dog model indicates that there is a species difference in the amount of RPE65 required to drive the visual cycle and that the demand for RPE65 in affected persons was not met to the extent required for a durable, robust effect. (Funded by the National Institute for Health Research and others; ClinicalTrials.gov number, NCT00643747.).

Whole-Exome Sequencing Identifies Mutations in GPR179 Leading to Autosomal-Recessive Complete Congenital Stationary Night Blindness

Congenital stationary night blindness (CSNB) is a heterogeneous retinal disorder characterized by visual impairment under low light conditions. This disorder is due to a signal transmission defect from rod photoreceptors to adjacent bipolar cells in the retina. Two forms can be distinguished clinically, complete CSNB (cCSNB) or incomplete CSNB; the two forms are distinguished on the basis of the affected signaling pathway. Mutations in NYX, GRM6, and TRPM1, expressed in the outer plexiform layer (OPL) lead to disruption of the ON-bipolar cell response and have been seen in patients with cCSNB. Whole-exome sequencing in cCSNB patients lacking mutations in the known genes led to the identification of a homozygous missense mutation (c.1807C>T [p.His603Tyr]) in one consanguineous autosomal-recessive cCSNB family and a homozygous frameshift mutation in GPR179 (c.278delC [p.Pro93Glnfs(∗)57]) in a simplex male cCSNB patient. Additional screening with Sanger sequencing of 40 patients identified three other cCSNB patients harboring additional allelic mutations in GPR179. Although, immunhistological studies revealed Gpr179 in the OPL in wild-type mouse retina, Gpr179 did not colocalize with specific ON-bipolar markers. Interestingly, Gpr179 was highly concentrated in horizontal cells and Müller cell endfeet. The involvement of these cells in cCSNB and the specific function of GPR179 remain to be elucidated.

Genetic screening of LCA in Belgium: predominance of CEP290 and identification of potential modifier alleles in AHI1 of CEP290‐related phenotypes

Leber Congenital Amaurosis (LCA), the most severe inherited retinal dystrophy, is genetically heterogeneous, with 14 genes accounting for 70% of patients. Here, 91 LCA probands underwent LCA chip analysis and subsequent sequencing of 6 genes (CEP290, CRB1, RPE65, GUCY2D, AIPL1and CRX), revealing mutations in 69% of the cohort, with major involvement of CEP290 (30%). In addition, 11 patients with early‐onset retinal dystrophy (EORD) and 13 patients with Senior‐Loken syndrome (SLS), LCA‐Joubert syndrome (LCA‐JS) or cerebello‐oculo‐renal syndrome (CORS) were included. Exhaustive re‐inspection of the overall phenotypes in our LCA cohort revealed novel insights mainly regarding the CEP290‐related phenotype. The AHI1 gene was screened as a candidate modifier gene in three patients with the same CEP290 genotype but different neurological involvement. Interestingly, a heterozygous novel AHI1 mutation, p.Asn811Lys, was found in the most severely affected patient. Moreover, AHI1 screening in five other patients with CEP290‐related disease and neurological involvement revealed a second novel missense variant, p.His758Pro, in one LCA patient with mild mental retardation and autism. These two AHI1 mutations might thus represent neurological modifiers of CEP290‐related disease.

Perinatal growth characteristics and associated risk of developing threshold retinopathy of prematurity.

PURPOSE To document perinatal growth characteristics in infants who developed threshold retinopathy of prematurity (ROP) in an attempt to describe prenatal and postnatal growth-related risk factors for threshold ROP. METHODS To document birth weight as well as absolute and relative weight gain (g/d and g/kg/d) in the first 6 weeks of life in infants who developed threshold ROP and who were admitted to a single tertiary neonatal intensive care unit between 1996 and 2000. These data were compared (case-control approach) with infants of the same gestational age (GA) who did not developed threshold ROP. RESULTS Small for gestational age (SGA; ie, weight <10th percentile for a given GA) and growth restriction (<25th percentile for a given GA) are risk factors for threshold ROP (relative risk = 3.7 and 4.5, respectively). Absolute weight gain (g/d) is also associated with an increased risk of developing threshold ROP (P<.05). In contrast, relative weight gain (g/kg/d) is not significantly different between threshold ROP infants and GA-matched controls. CONCLUSIONS SGA and a birth weight below the 25(th) percentile are risk factors for threshold ROP. Postnatal weight and absolute weight gain (g and g/d, respectively) in the first 6 weeks of life are statistically significant but of less clinical relevance because smaller infants at birth stay relatively smaller during the first 6 weeks of life. Even with normal (ie, same weight as control infants) postnatal relative weight gain (g/kg/d), growth retarded or restricted infants at birth still have an increased risk of developing threshold ROP.

Integrity of the inferior longitudinal fasciculus and impaired object recognition in children: a diffusion tensor imaging study

Aim  In this study, we explored the integrity of the inferior longitudinal fasciculus (ILF) by means of diffusion tensor imaging tractography in children with visual perceptual impairment, and more specifically, object recognition deficits, compared with typically developing children.

Autosomal-dominant microtia linked to five tandem copies of a copy-number-variable region at chromosome 4p16.

Recently, large-scale benign copy-number variations (CNVs)--encompassing over 12% of the genome and containing genes considered to be dosage tolerant for human development--were uncovered in the human population. Here we present a family with a novel autosomal-dominantly inherited syndrome characterized by microtia, eye coloboma, and imperforation of the nasolacrimal duct. This phenotype is linked to a cytogenetically visible alteration at 4pter consisting of five copies of a copy-number-variable region, encompassing a low-copy repeat (LCR)-rich sequence. We demonstrate that the approximately 750 kb amplicon occurs in exact tandem copies. This is the first example of an amplified CNV associated with a Mendelian disorder, a discovery that implies that genome screens for genetic disorders should include the analysis of so-called benign CNVs and LCRs.

The Safety and Efficacy of Glaucoma Medication in the Pediatric Population

Topical glaucoma medications are widely used for childhood glaucoma, although little is known concerning the use of the newer glaucoma medications in this population. The majority of the references cited were extracted from PubMed. A literature review of all English language reports related to glaucoma medication in the pediatric population since 1980 was performed. Medical therapy of pediatric glaucoma contains four groups of drugs: beta-blockers (timolol and betaxolol), carbonic anhydrase inhibitors (dorzolamide), alpha2-agonists (brimonidine), and prostaglandin analogs (latanoprost). Timolol is the first choice in pediatric glaucoma. In cases with insufficient reduction of the intraocular pressure (IOP), the combination of timolol once a day and dorzolamide twice a day brings about a good control of the IOP. Both medications are effective and well tolerated. The alpha2-agonists have more and potentially serious adverse effects in children and are contraindicated for children younger than 2 years of age. Latanoprost tends to be less effective in lowering IOP in children than in adults. However, no studies are reported where latanoprost is used in monotherapy. Additional study may further delineate this drugs role in treating pediatric glaucoma. The safety profile of latanoprost in children appears excellent.

Identity-by-descent–guided mutation analysis and exome sequencing in consanguineous families reveals unusual clinical and molecular findings in retinal dystrophy

Purpose:Autosomal recessive retinal dystrophies are clinically and genetically heterogeneous, which hampers molecular diagnosis. We evaluated identity-by-descent–guided Sanger sequencing or whole-exome sequencing in 26 families with nonsyndromic (19) or syndromic (7) autosomal recessive retinal dystrophies to identify disease-causing mutations.Methods:Patients underwent genome-wide identity-by-descent mapping followed by Sanger sequencing (16) or whole-exome sequencing (10). Whole-exome sequencing data were filtered against identity-by-descent regions and known retinal dystrophy genes. The medical history was reviewed in mutation-positive families.Results:We identified mutations in 14 known retinal dystrophy genes in 20/26 (77%) families: ABCA4, CERKL, CLN3, CNNM4, C2orf71, IQCB1, LRAT, MERTK, NMNAT1, PCDH15, PDE6B, RDH12, RPGRIP1, and USH2A. Whole-exome sequencing in single individuals revealed mutations in either the largest or smaller identity-by-descent regions, and a compound heterozygous genotype in NMNAT1. Moreover, a novel deletion was found in PCDH15. In addition, we identified mutations in CLN3, CNNM4, and IQCB1 in patients initially diagnosed with nonsyndromic retinal dystrophies.Conclusion:Our study emphasized that identity-by-descent–guided mutation analysis and/or whole-exome sequencing are powerful tools for the molecular diagnosis of retinal dystrophy. Our approach uncovered unusual molecular findings and unmasked syndromic retinal dystrophies, guiding future medical management. Finally, elucidating ABCA4, LRAT, and MERTK mutations offers potential gene-specific therapeutic perspectives.Genet Med 16 9, 671–680.

Blau syndrome: cross-sectional data from a multicentre study of clinical, radiological and functional outcomes

OBJECTIVE To report baseline articular, functional and ocular findings of the first international prospective cohort study of Blau syndrome (BS). METHODS Three-year, multicentre, observational study on articular, functional (HAQ, Childhood HAQ and VAS global and pain), ophthalmological, therapeutic and radiological data in BS patients. RESULTS Baseline data on the first 31 recruited patients (12 females and 19 males) from 18 centres in 11 countries are presented. Of the 31 patients, 11 carried the p.R334W NOD2 mutation, 9 the p.R334Q and 11 various other NOD2 missense mutations; 20 patients were sporadic and 11 from five BS pedigrees. Median disease duration was 12.8 years (1.1-57). Arthritis, documented in all but one patient, was oligoarticular in 7, polyarticular in 23. The median active joint count was 21. Functional capacity was normal in 41%, mildly impaired in 31% and moderate-severe in 28% of patients. The most frequently involved joints at presentation were wrists, ankles, knees and PIPs. On radiographs, a symmetrical non-erosive arthropathy was shown. Previously unknown dysplastic bony changes were found in two-thirds of patients. Ocular disease was documented in 25 of 31 patients, with vitreous inflammation in 64% and moderate-severe visual loss in 33%. Expanded manifestations (visceral, vascular) beyond the classic clinical triad were seen in 52%. CONCLUSION BS is associated with severe ocular and articular morbidity. Visceral involvement is common and may be life-threatening. Bone dysplastic changes may show diagnostic value and suggest a previously unknown role of NOD2 in bone morphogenesis. BS is resistant to current drugs, suggesting the need for novel targeted therapies.

Empty sella, growth hormone deficiency and pseudotumour cerebri: effect of initiation, withdrawal and resumption of growth hormone therapy

Abstract An 11- year-old boy with normal visus and eye fundus, but with empty sella, growth hormone (GH) deficiency and central diabetes insipidus was found to have intracranial hypertension with papilloedema after 6 months of catch-up growth under recombinant human GH (rhGH) replacement therapy. Withdrawal of rhGH therapy was associated with normalisation of intra‐cranial␣pressure within 1 week. Three months later, resumption of rhGH therapy at a lower dose was again followed by pronounced growth acceleration, but now without papilloedema. Conclusion Children with empty sella and GH deficiency may be prone to rhGH-induced pseudotumour cerebri which appears to be rapidly reversible and dose-dependent.