Predictive genetic testing in minors for Myocilin juvenile onset open angle glaucoma.

Myocilin glaucoma is an autosomal dominant disorder leading to irreversible blindness, but early intervention can minimize vision loss and delay disease progression. The purpose of this study was to discuss the benefits of predictive genetic testing in minors for Myocilin mutations associated with childhood onset glaucoma. Three families with Myocilin mutations associated with an age of onset before 18 years and six unaffected at-risk children were identified. Predictive genetic testing was discussed with the parents and offered for at-risk minors. Parents opted for genetic testing in half of the cases. None carried the familial mutation. The age of disease onset in the family, the severity of the condition, and the age of the child are all factors that appear to influence the decision of the parent to test their children. Predictive genetic testing for early onset Myocilin glaucoma can facilitate early detection of disease or discharge from routine ophthalmic examinations.

The genetics of central corneal thickness.

Evidence in the recent literature has highlighted the importance of central corneal thickness (CCT) in relation to several ocular and non-ocular conditions. Most notably, thinner CCT has been identified as a risk factor for open-angle glaucoma. Despite having an extensive knowledge of the structure and function of the cornea, little is known about the pathways that determine CCT. There are data to suggest however that CCT has a strong genetic component. Heritability studies conducted in twins and family pedigrees indicate that CCT is one of the most highly heritable human traits, whereas data from a diverse range of ethnic groups show clear ethnic-related differences in CCT. Extreme CCT measurements have also been associated with rare genetic diseases. Although there is strong evidence supporting a genetic component to normal CCT variation, to date, no genes have been identified. This review investigates the current literature surrounding this topic and explores the significance of understanding the genetics of CCT and how this might benefit the field of open-angle glaucoma treatment and research.

Mortality in primary open-angle glaucoma: 'two cupped discs and a funeral'.

PURPOSE: The aim of this study was to investigate the causes of mortality in individuals with open-angle glaucoma (OAG). METHODS: All-cause mortality data from the Registry of Births, Deaths and Marriages for the Australian state of Tasmania, for all people who were at least 40 years of age at the time of death, were classified using International Classification of Diseases-10 guidelines. This information was cross-referenced to identify participants in the Glaucoma Inheritance Study in Tasmania (GIST) who had died. Contingency tables were used for crude analysis and then models were constructed, adjusting for age at death as well as gender. RESULTS: Between 1996 and 2005, a total of 33 879 deaths were recorded. Data were unavailable for 4868 (14.4%) people. The mean age at death for the study sample was 78.4+/-11.5 (range 41-109) years. Of those cases known to have OAG by their participation in GIST (n=2409), full mortality data were available for 741 (92.0%). Following adjustment for the age at death and male gender, the odds ratio for death due to ischaemic heart disease in people with OAG compared to the general population not known to have OAG was significant (OR=1.30, 95% CI: 1.08-1.56; P=0.006). Crude analysis revealed that there were significantly fewer people with OAG who died due to metastatic cancer (P<0.001); however, this did not remain significant following adjustment for age and gender. CONCLUSION: The pathoaetiological relationship between OAG and ischaemic heart disease is unclear and requires further investigation. Increased awareness of the association between cardiovascular disease and OAG is warranted.

Diabetic retinopathy is not associated with carbonic anhydrase gene polymorphisms.

PURPOSE: Carbonic anhydrase is elevated in the vitreous of patients with proliferative diabetic retinopathy (PDR). This study aimed to determine if common polymorphisms in the carbonic anhydrase (CA) gene influence susceptibility to diabetic retinopathy (DR). METHODS: In this multicentered study, a total of 235 control subjects with no DR, 158 subjects with nonproliferative DR (NPDR), 132 with proliferative DR (PDR), and 93 with clinically significant macular edema (CSME) were recruited. Blinding DR was defined as severe NPDR, PDR or CSME. DR subjects were drawn from both type 1 diabetes mellitus (T1DM) and type 2 diabetes mellitus (T2DM) populations. Ten tag single nucleotide polymorphisms were selected to cover the majority of genetic diversity across the CA gene. RESULTS: After adjustments were made for sex, disease duration, and HbA(1)c, no associations were found between any CA polymorphisms or haplotypes with any type of retinopathy in T1DM or T2DM. CONCLUSIONS: Sequence variation in CA is not associated with the risk of developing retinopathy in T1DM or T2DM and increases the likelihood that elevated vitreous CA may be a consequence rather than cause of DR. Further genetic studies are required to have a better understanding of the pathogenesis of this debilitating diabetic complication.

Advances in telemetric continuous intraocular pressure assessment.

With an ageing population showing an increasing prevalence of glaucoma, there is a pressing demand for continuous intraocular pressure (IOP) measurements which could surpass clinic-based measurements such as routine applanation tonometry. Glaucoma patients have fluctuations in IOP, and it has been proposed that these fluctuations are relevant to glaucoma progression. In addition, interindividual and intraindividual variation in corneal thickness and rigidity can lead to significant and poorly quantitated errors in applanation-based methods of estimating IOP. Microelectrical mechanical systems and complementary metal oxide semiconductor-based technology has enabled the development of smart miniaturised devices by augmenting the computational ability of microelectronics with capabilities of microsensors and microactuators. This review addresses various sensor technologies and both invasive and non-invasive approaches to the measurement of IOP. Advances in wireless communication (telemetry) between the implanted sensors and the external readout device are reviewed. In addition, biocompatibility of implantable sensors is discussed.

The natural history of OPA1-related autosomal dominant optic atrophy.

BACKGROUND/AIMS: Autosomal dominant optic atrophy (ADOA) is a genetically heterogenous disease. However, a large proportion of this disease is accounted for by mutations in OPA1. The aim of this longitudinal study was to investigate disease progression in Australian ADOA patients with confirmed OPA1 mutations. METHODS: Probands with characteristic clinical findings of ADOA were screened for OPA1 mutations, and relatives of identified mutation carriers were invited to participate. Disease progression was determined by sequential examination or using historical records over a mean of 9.6 (range 1-42) years. RESULTS: OPA1 mutation carriers (n = 158) were identified in 11 ADOA pedigrees. Sixty-nine mutation carriers were available for longitudinal follow-up. Using the right eye as the default, best-corrected visual acuity (BCVAR) remained unchanged (defined as visual acuity at or within one line of original measurement) in 43 patients (62%). BCVAR worsened by 2 lines in 13 patients (19%). BCVAR deteriorated by more than 2 lines in six patients (9%). Ten per cent of patients had an improvement in visual acuity. Mean time to follow-up was 9.6 years with the mean visual acuity being 6/18 for both the initial and subsequent measurements. There was no statistical significance in the rate of BCVAR loss across different OPA1 mutations (p = 0.55). CONCLUSION: OPA1-related ADOA generally progresses slowly and functional visual acuity is usually maintained. Longitudinal disease studies are important to enable appropriate counselling of patients. This study enables a better understanding of the natural history of ADOA.

Prevalence of CYP1B1 mutations in Australian patients with primary congenital glaucoma.

Analysis of CYP1B1 in primary congenital glaucoma (PCG) patients from various ethnic populations indicates that allelic heterogeneity is high, and some mutations are population specific. No study has previously reported the rate or spectrum of CYP1B1 mutations in Australian PCG patients. The aim of this study is to determine the frequency of CYP1B1 mutations in our predominately Caucasian, Australian cohort of PCG cases. Thirty-seven probands were recruited from South-Eastern Australia, along with 100 normal control subjects. Genomic DNA was extracted and the coding regions of CYP1B1 analysed by direct sequencing. Sequence analysis identified 10 different CYP1B1 disease-causing variants in eight probands (21.6%). Five subjects were compound heterozygotes, two subjects heterozygous and one homozygous for CYP1B1 mutations. Three missense mutations are novel (D192Y, G329D, and P400S). None of the novel mutations identified were found in normal controls. One normal control subject was heterozygous for the previously reported CYP1B1 R368H mutation. Six previously described probable polymorphisms were also identified. Mutations in CYP1B1 account for approximately one in five PCG cases from Australia. Our data also supported the high degree of allelic heterogeneity seen in similar studies from other ethnic populations, thereby underscoring the fact that other PCG-related genes remain to be identified.

The role of the Met98Lys optineurin variant in inherited optic nerve diseases.

AIMS: To investigate the role of the common OPTN Met98Lys variant as a risk allele in open-angle glaucoma (OAG), autosomal dominant optic atrophy (ADOA) and Leber's hereditary optic neuropathy (LHON). METHODS: The presence of the Met98Lys variant was determined in a total of 498 (128 with normal-tension glaucoma (NTG)) patients with OAG, 29 patients who had myocilin-related OAG, 101 patients from ADOA pedigrees, 157 patients from LHON pedigrees and 218 examined OAG age-matched normal controls. RESULTS: 17 of 218 (7.8%) controls had the Met98Lys variant. 28 (5.6%) patients with OAG were Met98Lys positive. More Met98Lys carriers were found in the NTG group than in the high-tension glaucoma (HTG) group (p = 0.033). However, no significant difference was observed between the NTG and control cohorts (p = 0.609). Two MYOC mutation carriers were found to have the variant. The variant was found in 1 of 10 pedigrees with ADOA and in 8 of 35 pedigrees with LHON. CONCLUSION: Data from this study do not support a strong role for the OPTN Met98Lys variant in glaucoma, ADOA or LHON. However, a weak association was observed of the variant with NTG compared with that with HTG. Meta-analysis of all published data on the variant and glaucoma confirmed that the association, although weak, is highly statistically significant in the cohort with glaucoma versus controls.

Nail-patella syndrome and its association with glaucoma: a review of eight families.

BACKGROUND: Nail-patella syndrome (NPS) is a rare autosomal dominant syndrome, characterised by dysplasia of the nails, patellae, elbows and iliac horns. Mutations in the LMX1B gene were found in four North American families in whom glaucoma cosegregated with NPS. AIMS: To investigate the association of glaucoma with NPS in Australian families and to determine how common NPS is in Australia. METHODS: One family with NPS and glaucoma was identified from the Glaucoma Inheritance Study in Tasmania. A further 18 index cases of NPS were identified from the genetics database for southeastern Australia. Eight of these pedigrees were available for comprehensive glaucoma examination on available family members. DNA was sequenced for mutations in LMX1B. RESULTS: In total, 52 living cases of NPS were identified suggesting a minimum prevalence of at least 1 in 100 000. 32 subjects from eight NPS pedigrees (four familial and four sporadic cases) were examined. 14 subjects had NPS alone. 4 subjects had NPS and glaucoma or ocular hypertension. Five pedigrees with NPS had a reported family history of glaucoma, although some of these people with glaucoma did not have NPS. LMX1B mutations were identified in 5 of the 8 index cases-three sporadic and two familial. Two of the six (33%) participants over 40 years of age had developed glaucoma, showing increased risk of glaucoma in NPS. CONCLUSION: Patients with NPS should be examined regularly for glaucoma. However, because the families with NPS are ascertained primarily from young probands or probands who are isolated cases, the exact level of risk is unclear.

Lack of association of p53 polymorphisms and haplotypes in high and normal tension open angle glaucoma.

BACKGROUND: The final common pathway for open angle glaucoma (OAG) is retinal ganglion cell apoptosis. Polymorphisms in p53, a major regulator of apoptosis, affect the efficiency of cell death induction. Association studies of p53 haplotypes and OAG have had conflicting results. OBJECTIVE: To examine the association between p53 haplotypes and OAG in a larger white population than in previous reports, and extend the analysis to normal tension glaucoma. METHODS: 345 unrelated people with OAG were recruited (283 subjects with high tension glaucoma and 62 with normal tension glaucoma) and compared with 178 age matched controls. Genomic DNA was analysed for the p53 codon 72 Arg/Pro polymorphism as well as for the presence or absence of a 16 bp intron 3 insertion. RESULTS: In this white cohort no association was found between glaucoma (high or normal tension) and either sequence variant or haplotype. CONCLUSIONS: The p53 codon 72 Arg/Pro polymorphism is not associated with age of onset or severity of glaucoma.

The telomere of human chromosome 1p contains at least two independent autosomal dominant congenital cataract genes.

AIMS: Multiple genetic causes of congenital cataract have been identified, both as a component of syndromes and in families that present with isolated congenital cataract. Linkage analysis was used to map the genetic locus in a six generation Australian family presenting with total congenital cataract. METHODS: Microsatellite markers located across all known autosomal dominant congenital cataract loci were genotyped in all recruited family members of the Tasmanian family. Both two point and multipoint linkage analysis were used to assess each locus under an autosomal dominant model. RESULTS: Significant linkage was detected at the telomere of the p arm of chromosome 1, with a maximum two point LOD of 4.21 at marker D1S507, a maximum multipoint exact LOD of 5.44, and an estimated location score of 5.61 at marker D1S507. Haplotype analysis places the gene inside a critical region between D1S228 and D1S199, a distance of approximately 6 megabases. The candidate gene PAX7 residing within the critical interval was excluded by direct sequencing in affected individuals. CONCLUSION: This is the third report of congenital cataract linkage to 1ptel. The critical region as defined by the shared haplotype in this family is clearly centromeric from the Volkmann cataract locus identified through study of a Danish family, indicating that two genes causing autosomal dominant congenital cataract map to the telomeric region of chromosome 1p.

Investigation of crystallin genes in familial cataract, and report of two disease associated mutations.

AIMS: Mutations of seven crystallin genes have been shown to cause familial cataract. The authors aimed to identify disease causing crystallin mutations in paediatric cataract families from south eastern Australia. METHODS: 38 families with autosomal dominant or recessive paediatric cataract were examined. Three large families were studied by linkage analysis. Candidate genes at regions providing significant LOD scores were sequenced. Single stranded conformational polymorphism (SSCP) analysis was used to screen five crystallin genes in the probands, followed by direct sequencing of observed electrophoretic shifts. Mutations predicted to affect the coding sequence were subsequently investigated in the entire pedigree. RESULTS: A LOD score of 3.72 was obtained at the gamma-crystallin locus in one pedigree. Sequencing revealed a P23T mutation of CRYGD, found to segregate with disease. A splice site mutation at the first base of intron 3 of the CRYBA1/A3 gene segregating with disease was identified by SSCP in another large family. Five polymorphisms were also detected. CONCLUSIONS: Although mutations in the five crystallin genes comprehensively screened in this study account for 38% of paediatric cataract mutations in the literature, only two causative mutations were detected in 38 pedigrees, suggesting that crystallin mutations are a relatively rare cause of the cataract phenotype in this population.

Retinopathy of prematurity: recent advances in our understanding.

Retinopathy of prematurity (ROP) has been recognised as an important cause of childhood visual impairment and blindness since the 1940s when improved facilities and treatment increased the survival rate of premature infants. Although its incidence and severity have been decreasing in developed countries over the past two decades, both are increasing in developing nations. ROP is consequently targeted as an important but avoidable disease. This review provides an updated summary and discussion of much of the work that has been produced through population, animal, cell culture, and genetic research. The authors examine the prevalence, risk factors, and possible causes of the disease with a particular focus on genetic studies. They conclude that while significant reductions in the disease have occurred in developed countries, further research is required to fully understand and prevent the disease. In the meantime, development and implementation of appropriate screening and treatment strategies will be critical in reducing blindness in developing countries.

Aetiology of congenital and paediatric cataract in an Australian population.

BACKGROUND/AIM: Paediatric cataract is a major cause of childhood blindness. Several genes associated with congenital and paediatric cataracts have been identified. The aim was to determine the incidence of cataract in a population, the proportion of hereditary cataracts, the mode of inheritance, and the clinical presentation. METHODS: The Royal Children's Hospital and the Royal Victorian Eye and Ear Hospital have a referral base for almost all paediatric patients with cataracts in south eastern Australia. The database contains cases seen over the past 25 years. The medical histories of these patients were reviewed. RESULTS: 421 patients with paediatric cataract were identified, which gives an estimated incidence of 2.2 per 10,000 births. Of the 342 affected individuals with a negative family history, 50% were diagnosed during the first year of life, and 56/342 (16%) were associated with a recognised systemic disease or syndrome. Unilateral cataract was identified in 178/342 (52%) of sporadic cases. 79 children (from 54 nuclear families) had a positive family history. Of these 54 families, 45 were recruited for clinical examination and DNA collection. Ten nuclear families were subsequently found to be related, resulting in four larger pedigrees. Thus, 39 families have been studied. The mode of inheritance was autosomal dominant in 30 families, X linked in four, autosomal recessive in two, and uncertain in three. In total, 178 affected family members were examined; of these 8% presented with unilateral cataracts and 43% were diagnosed within the first year of life. CONCLUSIONS: In the paediatric cataract population examined, approximately half of the patients were diagnosed in the first year of life. More than 18% had a positive family history of cataracts. Of patients with hereditary cataracts 8% presented with unilateral involvement. Identification of the genes that cause paediatric and congenital cataract should help clarify the aetiology of some sporadic and unilateral cataracts.

Retinopathy of prematurity: recent advances in our understanding.

Retinopathy of prematurity (ROP) has been recognised as an important cause of childhood visual impairment and blindness since the 1940s when improved facilities and treatment increased the survival rate of premature infants. Although its incidence and severity have been decreasing in developed countries over the past two decades, both are increasing in developing nations. ROP is consequently targeted as an important but avoidable disease. This review provides an updated summary and discussion of much of the work that has been produced through population, animal, cell culture, and genetic research. The authors examine the prevalence, risk factors, and possible causes of the disease with a particular focus on genetic studies. They conclude that while significant reductions in the disease have occurred in developed countries, further research is required to fully understand and prevent the disease. In the meantime, development and implementation of appropriate screening and treatment strategies will be critical in reducing blindness in developing countries.

Genetic factors in athetoid cerebral palsy.

Within the cerebral palsy syndromes, athetosis is most commonly causally associated with serious perinatal complications. Genetic factors are thought to play a lesser role, although the risk of recurrence in siblings has been suggested to be as high as 10%. We have conducted a clinical study of 22 subjects with a diagnosis of athetoid cerebral palsy and a review of the literature aiming to identify instances of familial recurrence of athetoid cerebral palsy. The birth history, family history, and previous investigations of subjects with athetoid cerebral palsy were studied and subjects were clinically examined for evidence of an underlying genetic etiology. Factors suggesting a genetic cause were specifically sought, such as advanced paternal age, progression of symptoms, and associated congenital abnormalities. No subjects in the study group had similarly affected relatives, and additional features suggesting a genetic cause were not observed. A literature search identified 16 instances of familial recurrence of athetoid cerebral palsy. Familial cases were typically associated with significant spasticity, microcephaly, intellectual disability, seizures, and a lack of history of birth asphyxia, and most could be explained by either autosomal-recessive or X-linked-recessive inheritance. The genetic contribution to athetoid cerebral palsy is small, with an overall risk of recurrence in siblings of about 1%. This risk is lower than previously suggested in the literature.

Evidence for genetic heterogeneity within eight glaucoma families, with the GLC1A Gln368STOP mutation being an important phenotypic modifier.

OBJECTIVE: To investigate the phenotype and age-related penetrance of primary open-angle glaucoma (POAG) in Australian families with the most common Myocilin mutation (Gln368STOP). DESIGN: Cross-sectional genetic study. PARTICIPANTS: Eight pedigrees carrying the Gln368STOP mutation were ascertained from 1730 consecutive cases of POAG in the Glaucoma Inheritance Study in Tasmania. METHODS: Index cases and available family members were examined for signs of glaucoma, and the presence of the GLC1A Gln368STOP mutation was ascertained by single-strand conformation polymorphism analysis and subsequent direct sequencing. RESULTS: From the eight pedigrees, 29 Gln368STOP mutation-carrying individuals with either ocular hypertension (OHT) or POAG were found, with a mean age at diagnosis of 52.4 +/- 12.9 years and a mean peak intraocular pressure (IOP) of 28.4 +/- 4.7 mmHg. A further 11 mutation carriers older than 40 years have been studied, who as yet show no signs of OHT or POAG. Within the 8 pedigrees, a further 31 individuals with OHT or POAG were identified who did not carry the Gln368STOP mutation. For these individuals the mean age at diagnosis was higher (62.3 +/- 13.7 years, P < 0.01), and the mean peak IOP was lower (25.4 +/- 6.4 mmHg, P = 0.01). For Gln368STOP carriers, age-related penetrance for OHT or POAG was 72% at age 40 years and 82% at age 65 years. A positive family history of POAG was present in all index cases. Five of the eight pedigrees had a positive family history on both maternal and paternal sides. Seven of the eight pedigrees had one or more individuals with POAG who did not carry the mutation. Eight of the 29 Gln368STOP carriers with OHT or POAG had undergone trabeculectomy. CONCLUSIONS: The GLC1A Gln368STOP mutation is associated with POAG, which in the pedigrees studied is of a younger age of onset and higher peak IOP than non-mutation glaucoma cases. In addition, Gln368STOP mutation glaucoma cases were more likely to have undergone glaucoma drainage surgery. We have not observed simple autosomal dominant inheritance patterns for POAG in these pedigrees. Other factors, as yet uncharacterized, are involved in expression of the POAG phenotype in Gln368STOP pedigrees.

Survival of nontypeable Haemophilus influenzae in macrophages.

In this study we have investigated the ability of nonencapsulated, nontypeable Haemophilus influenzae, NT477 to survive in the J774 mouse macrophage-like cell line. Viable, intracellular nontypeable H. influenzae could still be recovered from macrophages 72 h after phagocytosis. In contrast, H. influenzae strain Rd, an avirulent, nonencapsulated variant of a serotype d strain, was killed within 24 h. These differences suggest that NT477, in comparison to Rd, possesses unique attributes that enable it to survive in macrophages for prolonged periods. To determine whether this trait is ubiquitous amongst nontypeable H. influenzae, 33 primary clinical isolates obtained from children with otitis media were screened for their ability to survive in macrophages. Of these isolates, 82% were able to persist in an intracellular environment for periods of at least 24 h. The number of viable organisms recovered at this time ranged from 2x10(4) to 50 colony-forming units per strain indicating that the extent to which nontypeable H. influenzae can resist macrophage-mediated killing varies between strains.