Variants in myelin regulatory factor (MYRF) cause autosomal dominant and syndromic nanophthalmos in humans and retinal degeneration in mice

Nanophthalmos is a rare, potentially devastating eye condition characterized by small eyes with relatively normal anatomy, a high hyperopic refractive error, and frequent association with angle closure glaucoma and vision loss. The condition constitutes the extreme of hyperopia or farsightedness, a common refractive error that is associated with strabismus and amblyopia in children. NNO1 was the first mapped nanophthalmos locus. We used combined pooled exome sequencing and strong linkage data in the large family used to map this locus to identify a canonical splice site alteration upstream of the last exon of the gene encoding myelin regulatory factor (MYRF c.3376-1G>A), a membrane bound transcription factor that undergoes autoproteolytic cleavage for nuclear localization. This variant produced a stable RNA transcript, leading to a frameshift mutation p.Gly1126Valfs*31 in the C-terminus of the protein. In addition, we identified an early truncating MYRF frameshift mutation, c.769dupC (p.S264QfsX74), in a patient with extreme axial hyperopia and syndromic features. Myrf conditional knockout mice (CKO) developed depigmentation of the retinal pigment epithelium (RPE) and retinal degeneration supporting a role of this gene in retinal and RPE development. Furthermore, we demonstrated the reduced expression of Tmem98, another known nanophthalmos gene, in Myrf CKO mice, and the physical interaction of MYRF with TMEM98. Our study establishes MYRF as a nanophthalmos gene and uncovers a new pathway for eye growth and development.

Severe Guillain-Barré syndrome following primary infection with varicella zoster virus in an adult

Varicella zoster virus (VZV) infection may trigger Guillain-Barré syndrome (GBS), but this is rare and almost always in the context of reactivation disease from latent VZV, 'shingles'. We report here a case of severe GBS following primary VZV infection in an adult. A 40-year-old man of Indian origin developed features of GBS including quadriplegia, bulbar paralysis, and bilateral facial nerve palsies 14 days after primary VZV infection contracted from a known case in a family member. Nerve conduction studies confirmed acute inflammatory demyelinating polyneuropathy. Anti-ganglioside antibodies were negative. The mechanism of Schwann cell attack following VZV infection is poorly understood but this case suggests that primary VZV infection may be a sufficient stimulus to drive antibody generation and precipitate severe clinical symptomatology. The morbidity associated with the complications of VZV infection in adulthood could be avoided if patients who are seronegative for VZV (frequently from the Asian subcontinent) are offered prophylaxis after an exposure in adulthood.

Variation in optineurin (OPTN) allele frequencies between and within populations

PURPOSE

To evaluate the extent to which mutations in the optineurin (OPTN) glaucoma gene play a role in glaucoma in different populations.

METHODS

Case-controlled study of OPTN sequence variants in individuals with or without glaucoma in populations of different ancestral origins and evaluate previous OPTN reports. We analyzed 314 subjects with African, Asian, Caucasian and Hispanic ancestries included 229 cases of primary open-angle glaucoma, 51 cases of juvenile-onset open-angle glaucoma, 33 cases of normal tension glaucoma, and 371 controls. Polymerase chain reaction-amplified OPTN coding exons were resequenced and case frequencies were compared to frequencies in controls matched for ancestry.

RESULTS

The E50K sequence variant was identified in one individual from Chile with normal tension glaucoma, and the 691_692insAG variant was found in one Ashkenazi Jewish individual from Russia. The R545Q variant was found in two Asian individuals with primary open-angle glaucoma; one of Filipino ancestry and one of Korean ancestry. In addition to presenting OPTN allele frequencies for Caucasian and Asian populations that have been the subject of previous reports, we also present information for populations of Hispanic and black African ancestries.

CONCLUSIONS

Our study contributes additional evidence to support the previously reported association of the OPTN E50K mutation with glaucoma. After finding an additional 691_692insAG OPTN variant, we can still only conclude that this variant is rare. Combined analysis of our data with data from more than a dozen other studies indicates no association of R545Q with glaucoma in most populations. Those same studies disagree in their conclusions regarding the role of M98K in glaucoma. Our analysis of the combined data provides statistically significant evidence of association of M98K with normal tension glaucoma in Asian populations, but not in Caucasian populations; however, the validity of this conclusion is questionable because of large differences in allele frequencies between and within populations. It is currently not possible to tell how much of the underlying cause of the allele frequency difference is attributable to demographic, technical, or ascertainment differences among the studies.

Estimation of ranolazine and eleven phase I metabolites in human plasma by liquid chromatography-atmospheric pressure chemical ionisation mass spectrometry with selected-ion monitoring

The estimation of ranolazine, a novel piperazine derivative, and eleven of its Phase I metabolites has been undertaken by liquid chromatography-atmospheric pressure chemical ionisation mass spectrometry (LC-APCI-MS). Plasma samples, taken on day 5 of a multiple-dose study, were extracted by solid-phase extraction (SPE) and analysed, using a gradient HPLC system coupled to the APCI source of a Finnigan MAT TSQ 700 mass spectrometer. Metabolites were analysed in selected-ion monitoring (SIM) mode, using an instrument control language (ICL) procedure. The LC-MS combination allowed resolution of all eleven metabolites, including four hydroxylated metabolites and five unresolved components. The results from the linear regression showed good correlation (r2 > 0.980) for all the metabolites. Plasma concentrations indicated that three metabolites were present at levels higher than 10% of the parent compound.

The characterization of the metabolites of ranolazine in man by liquid chromatography mass spectrometry

The metabolism of ranolazine (RS-43285) or (+)N-(2,6-dimethylphenyl)-4[2-hydroxy-3-(2-methoxyphenoxy)-propyl]-1- piperazine acetamide dihydrochloride was investigated in man using plasma samples obtained from four different clinical studies. The metabolite profiles following single and multiple doses of 342 mg instant release (IR) ranolazine, following multiple doses of 1000 mg sustained release (SR) ranolazine and following dosing with both ranolazine (IR) and a potentially co-administered drug, diltiazem, were compared. Metabolism of ranolazine in man was shown by LC/MS analysis to be extensive with up to seven primary routes of metabolism identified. N-dealkylation by hydrolysis at the piperazine ring produced three metabolites whilst O-demethylation and O-dearylation at the methoxyphenoxy moiety produced a further two compounds. Additionally, hydrolysis of the amide group formed one other species. Oxygenation at various points in the molecule produced a further four metabolites. Direct conjugation of ranolazine with glucuronic acid and with an uncharacterized adduct were also identified as a route of elimination. Ten other biotransformation products were formed as a result of multiple metabolic steps. Conjugation was also associated with the desmethyl metabolite (glucuronide and unidentified conjugates) of hydroxylated ranolazine. In a previous publication (Journal of Chromatography, 1995, accepted for publication) semi-quantitative analyses of pooled plasma from the study where ranolazine was dosed at 1000 mg twice daily showed that of the twelve metabolites studied only four accounted for AUC's in excess of 10% of the ranolazine AUC.

Growth in the first summer of life: a comparisson of nine co-occurring fish species

Growth in the first summer of life was compared in nine coexisting fish species with different life history strategies. Relative to hatching size, the various species grew 6- to 10-fold in length and up to 1000-fold in weight. Growth patterns were similar among species; length increments were linear early in the summer and reached a plateau by early September. Few species grew significantly in length or weight beyond September. There were also few appreciable differences in length–weight regressions among species, and in all cases growth was isometric. Spawning date had the greatest influence on the amount of growth attained, with early spawners achieving a greater mean length and weight than late spawners. Adult size did not influence the amount of growth; large-bodied species achieved proportionately less of their adult weight and length in the first summer than did small species. However, adult size did influence the duration of the spawning period. Small-bodied species had the most protracted spawning seasons and the greatest size range of young at the end of the summer. There was no apparent relationship between diet type and growth in young fish.