Retinal degeneration associated with RDH12 mutations results from decreased 11-cis retinal synthesis due to disruption of the visual cycle

Retinoid dehydrogenases/reductases catalyze key oxidation-reduction reactions in the visual cycle that converts vitamin A to 11-cis retinal, the chromophore of the rod and cone photoreceptors. It has recently been shown that mutations in RDH12, encoding a retinol dehydrogenase, result in severe and early-onset autosomal recessive retinal dystrophy (arRD). In a cohort of 1011 individuals diagnosed with arRD, we have now identified 20 different disease-associated RDH12 mutations, of which 16 are novel, in a total of 22 individuals (2.2%). Haplotype analysis suggested a founder mutation for each of the three common mutations: p.L99I, p.T155I and c.806_810delCCCTG. Patients typically presented with early disease that affected the function of both rods and cones and progressed to legal blindness in early adulthood. Eleven of the missense variants identified in our study exhibited profound loss of catalytic activity when expressed in transiently transfected COS-7 cells and assayed for ability to convert all-trans retinal to all-trans retinol. Loss-of-function appeared to result from decreased protein stability, as expression levels were significantly reduced. For the p.T49M variant, differing activity profiles were associated with each of the alleles of the common p.R161Q RDH12 polymorphism, suggesting that genetic background may act as a modifier of mutation effect. A locus (LCA3) for Leber congenital amaurosis, a severe, early-onset form of arRD, maps close to RDH12 on chromosome 14q24. Haplotype analysis in the family in which LCA3 was mapped excluded RDH12 as the LCA3 gene and thus suggests the presence of a novel arRD gene in this region.     

Contrast enhancement of the retinal image and image distortion associated with macular degeneration

An analysis of image distortion in connection with macular degeneration revealed that seeing objects requires brightness contrast enhancement. Thus macular degeneration changes neural interaction controlling bipolar cell responses to light stimulating photoreceptors to reverse spatial brightness contrast enhancement with the consequence that objects cannot be seen. This shows that the contrast of the retinal images is too low for vision without enhancement. However images consisting of randomly arranged small spots of different brightness are seen because of cones enhancing bipolar cell responses to rod input and rods enhancing bipolar cell responses to cone input. This residual vision and the observation that image distortion disappears at low light intensities reveal that macular degeneration is a functional disorder with intact photoreceptor function. The affection may therefore be caused by a reduction of blood flow through the choriocapillaries associated with ageing. The analysis of image distortion associated with the affection led to a simple way to determine the size of the affected retinal area, making it possible to follow the progression of the affection in a direct and simple way. Basic aspects are described of synaptic interaction within the information processing unit that determines the responses of the bipolar cells to photoreceptor input. This unit is the first information processing unit that has been revealed thanks to the extension of the analysis of the nervous system to the nanometer level at which information is processed. The minute size of the information processing unit, the special conditions for synaptic transmission combined with the short distances separating the synapses create special conditions for neural interaction at the nanometer level, establishing conditions for high speed neural communication.     

Expanding the phenotype associated with biallelic WDR60 mutations: Siblings with retinal degeneration and polydactyly lacking other features of short rib thoracic dystrophies

Ciliopathies are disorders of the primary cilium that can affect almost all organs and that are characterized by pleiotropy and extensive intra‐ and interfamilial phenotypic variability. Accordingly, mutations in the same gene can cause different ciliopathy phenotypes of varying severity. WDR60 encodes a protein thought to play a role in the primary cilium's intraflagellar transport machinery. Mutations in this gene are a rare cause of Jeune asphyxiating thoracic dystrophy (JATD) and short‐rib polydactyly syndrome (SRPS). Here we report on a milder and distinct phenotype in a consanguineous Pakistani pedigree with two adolescent sisters affected by retinal degeneration and postaxial polydactyly, but lack of any further skeletal or chondrodysplasia features. By targeted high‐throughput sequencing of genes known or suspected to be involved in ciliogenesis, we detected a novel homozygous N‐terminal truncating WDR60 mutation (c.44delC/p.Ala15Glufs*90) that co‐segregated with the disease in the family. Our finding broadens the spectrum of WDR60‐related phenotypes and shows the utility of broad multigene panels during the genetic work‐up of patients with ciliopathies.

     

Rapid detection of point mutations of the Neisseria gonorrhoeae gyrA gene associated with decreased susceptibilities to quinolones.

Mutations in the gyrA gene resulting in amino acid changes at Ser-91 and Asp-95 are significantly associated with decreased susceptibilities to quinolones in Neisseria gonorrhoeae. To detect these mutations, we developed a rapid and simple assay based on amplification of the region of the gyrA gene containing the mutation sites by PCR and digestion of the PCR product with a restriction enzyme. A naturally occurring HinfI restriction site was present in the region containing the Ser-91 codon, and an artificial HinfI restriction site was created in the region containing the Asp-95 codon by the method of primer-specified restriction site modification. The mutations generating alterations at Ser-91 and Asp-95 were detected as restriction fragment length polymorphisms of the PCR products digested with HinfI. Fifty-five clinical strains of N. gonorrhoeae were examined for mutations in the gyrA gene by this method. Mutations at Ser-91 and/or Asp-95 were detected in all the 31 strains in which the mutations had been confirmed by DNA sequencing. Our method allows simultaneous testing of a large number of strains and provides results within 8 h. This rapid and simple assay could be a useful screening device for genetic alterations associated with decreased susceptibilities to quinolones in N. gonorrhoeae and could facilitate epidemiological studies on clinical isolates of N. gonorrhoeae with decreased susceptibilities to quinolones.     

Low negative affect prior to treatment is associated with a decreased chance of live birth from a first IVF cycle

BACKGROUND: Psychological variables, such as anxiety and depression, may have a negative impact on IVF outcomes, but the evidence remains inconclusive. Previous studies have usually measured a single psychological parameter with clinical pregnancy as the outcome. The objective of the current study was to determine whether pretreatment or procedural psychological variables in women undergoing a first IVF cycle affect the chance of achieving a live birth from that cycle. METHODS: Between February 2002 and February 2004, 391 women with an indication for IVF were recruited at two University Medical Centres in The Netherlands. Pretreatment anxiety and depression were measured with the Hospital Anxiety and Depression Scale. The Daily Record Keeping Chart was used to measure negative and positive affect before treatment and daily during ovarian stimulation. Multiple stepwise forward logistic regression analysis was performed with term live birth as the dependent variable. RESULTS: Regression analysis showed that women who expressed less negative affect at baseline were less likely to achieve live birth (P = 0.03). After one IVF cycle, women who received a standard IVF strategy were more likely to reach live birth delivery than those who received a mild IVF strategy (P = 0.002). A male/female indication for IVF was associated with a higher chance of achieving term live birth than a female only indication (P = 0.03). Age, duration of infertility or type of infertility were not independent predictors of live birth. CONCLUSIONS: The relationship between psychological parameters and IVF success rates is more complex than commonly believed. The expression of negative emotions before starting IVF might not be always detrimental for outcomes.     

Targeted disruption of the galectin-3 gene results in decreased susceptibility to multiple low dose streptozotocin-induced diabetes in mice

Galectin 3 (Gal-3) is an antiapoptotic and a proinflammatory lectin. We hypothesized that the proinflammatory properties of Gal-3 may influence disease induction in the multiple low doses of streptozotocin model of diabetes. Diabetes was induced in C57BL/6 Gal-3(+/+) and Gal-3(-/-) mice and disease monitored by blood glucose level, immuno-histology, insulin content of islets and expression of the proinflammatory cytokines, TNF-alpha, IFN-gamma, IL-17, and iNOS in pancreatic lymph nodes. Gal-3(+/+) mice developed delayed and sustained hyperglycemia, mononuclear cellular infiltration and reduced insulin content of islets accompanied with expression of proinflammatory cytokines. Gal-3(-)/(-) mice were relatively resistant to diabetogenesis as evaluated by glycemia, quantitative histology and insulin content. Further, we observed the weaker expression of IFN-gamma and complete absence of TNF-alpha, and IL-17 in draining pancreatic lymph nodes. Macrophages, the first cells that infiltrate the islet in this model of diabetes, produce less TNF-alpha and NO in Gal-3(-/-) mice. Thus, Gal-3 is involved in immune mediated beta cell damage and is required for diabetogenesis in this model of disease.     

Identification of novel mutations in the SEMA4A gene associated with retinal degenerative diseases

Semaphorins are a large family of transmembrane proteins. The gene for SEMA4A encodes a transmembrane protein comprising 760 amino acids. To investigate its association with human retinal degeneration, mutation screening of the SEMA4A gene was carried out on 190 unrelated patients suffering from a variety of eye diseases. We report the first observation of the involvement of SEMA4A gene mutations causing retinitis pigmentosa (RP) and cone rod dystrophy (CRD). We screened the DNA of 135 patients with RP, 25 patients with CRD, and 30 with LCA using SSCP and direct DNA sequencing for mutations in the SEMA4A gene. Two mutations, p.D345H and p.F350C, were observed only in affected patients; they were not observed in any of the normal members or the 100 control subjects. Both mutations identified occur in the conserved semaphorin domain. Multiple sequence alignments using Clustal analysis showed that R713Q is a conserved substitution and D345H is a semi‐conserved substitution. We conclude that these mutations are a cause of various retinal degenerations.     

Laboratory detection of Haemophilus influenzae with decreased susceptibility to nalidixic acid, ciprofloxacin, levofloxacin, and moxifloxacin due to GyrA and ParC mutations

The detection of clinical isolates with decreased fluoroquinolone susceptibilities and a resistance mechanism is of epidemiological and clinical interest. We studied the susceptibilities of 62 clinical isolates and 2 American Type Culture Collection reference strains of Haemophilus influenzae to ciprofloxacin, levofloxacin, moxifloxacin, and nalidixic acid by the microdilution and disk diffusion methods. The ciprofloxacin MICs for 34 of the isolates were >/=0.12 micro g/ml (range, 0.12 to 32 micro g/ml), and the ciprofloxacin MICs for 28 matched control isolates were /=0.5 micro g/ml and the vast majority of those for which nalidixic acid MICs were >/=32 micro g/ml exhibited amino acid changes in GyrA and ParC. Nalidixic acid and the other three fluoroquinolones studied could be used to screen H. influenzae isolates for the detection of decreased susceptibilities to quinolones due to the acquisition of two amino acid changes in the QRDRs of GyrA and ParC (sensitivity, >95%; specificity, >80%).     

Sulfonylurea therapy in two Korean patients with insulin-treated neonatal diabetes due to heterozygous mutations of the KCNJ11 gene encoding Kir6.2

Permanent neonatal diabetes (PND) is a rare form of diabetes characterized by insulin-requiring hyperglycemia diagnosed within the first three months of life. In most cases, the causes are not known. Recently, mutations in the KCNJ11 gene encoding the Kir6.2 subunit of the ATP-sensitive K+ channel have been described in patients with PND. We report the first two Korean cases with PND due to a lysineto- arginine substitution at position 170 (K179R) and a valine-to-methionine substitution at position 59 (V59M) mutations of KCNJ11 encoding Kir6.2, respectively. After several years of insulin therapy, these patients were managed by oral glibenclamide therapy at a daily dose of 0.8-0.9 mg/kg. Their basal c-peptide levels increased after one week of glibenclamide therapy, and one month later, the insulin and c-peptide levels were in the normal ranges without any episodes of hyper- or hypoglycemia. These cases demonstrate that oral sulfonylurea may be the treatment of choice in PND patients with KCNJ11 mutations even at a young age.     

Impaired helix 12 dynamics due to proline 892 substitutions in the androgen receptor are associated with complete androgen insensitivity

Human Molecular Genetics (2006) 15, 921–931;     

Impaired helix 12 dynamics due to proline 892 substitutions in the androgen receptor are associated with complete androgen insensitivity

Structural studies of the ligand-binding domain (LBD) of several steroid receptors have revealed that the dynamic properties of the C-terminal helix 12 (H12) are the major determinant of the activation mode of these receptors. H12 exhibits high mobility and different conformations in the absence of ligand. Upon ligand binding, H12 is stabilized in a precise position to seal the ligand-binding pocket and finalize the assembly of the activation function (AF-2) domain. In this study, we investigated the role of the conserved proline 892 of the androgen receptor (AR) in directing the dynamic location and orientation of the AR-H12. We used a combined approach including kinetic and biochemical assays with molecular dynamic simulations to analyze two substitutions (P892A and P892L) identified in individuals with complete androgen insensitivity syndrome. Our analyses revealed distinct mechanisms by which these substitutions impair H12 function resulting in severely defective receptors. The AR-P892A receptor exhibited reduced ligand binding and transactivational potential because of an increased flexibility in H12. The AR-P892L substitution renders the receptor inactive due to a distorted, unstructured and misplaced H12. To confirm the mutants' inability to stabilize H12 in an active position, we have developed a novel in vivo assay to evaluate the accessibility of the H12-docking site on the AR-LBD surface. An extrinsic AR-H12 peptide was able to interact with wild-type and mutant LBDs in the absence of ligand. Ligand-induced proper positioning of the intrinsic H12 of wild-type AR prevented these interactions, whereas the misplacement of the mutants' H12 did not. Proline at this position may be critical for H12 dynamics not only in the AR, but also in other nuclear receptors where this proline is conserved.     

Duplication of part of 9q due to maternal 12;9 inverted insertion associated with pyloric stenosis

We report on a 9-month-old boy who had duplication of the long arm of chromosome 9 [46,XY, -12, +der(12) inv ins (12;9)(p13;q32q13)mat.]. The clinical manifestations of the patient were different from those seen in distal 9q duplication. Pyloric stenosis appears to be common in cases with proximal 9q duplications.     

R91W mutation in Rpe65 leads to milder early-onset retinal dystrophy due to the generation of low levels of 11-cis-retinal

RPE65 is a retinal pigment epithelial protein essential for the regeneration of 11-cis-retinal, the chromophore of cone and rod visual pigments. Mutations in RPE65 lead to a spectrum of retinal dystrophies ranging from Leber's congenital amaurosis to autosomal recessive retinitis pigmentosa. One of the most frequent missense mutations is an amino acid substitution at position 91 (R91W). Affected patients have useful cone vision in the first decade of life, but progressively lose sight during adolescence. We generated R91W knock-in mice to understand the mechanism of retinal degeneration caused by this aberrant Rpe65 variant. We found that in contrast to Rpe65 null mice, low but substantial levels of both RPE65 and 11-cis-retinal were present. Whereas rod function was impaired already in young animals, cone function was less affected. Rhodopsin metabolism and photoreceptor morphology were disturbed, leading to a progressive loss of photoreceptor cells and retinal function. Thus, the consequences of the R91W mutation are clearly distinguishable from an Rpe65 null mutation as evidenced by the production of 11-cis-retinal and rhodopsin as well as by less severe morphological and functional disturbances at early age. Taken together, the pathology in R91W knock-in mice mimics many aspects of the corresponding human blinding disease. Therefore, this mouse mutant provides a valuable animal model to test therapeutic concepts for patients affected by RPE65 missense mutations.     

Anxiety in the rat is associated with decreased release of 5-HT and glycine from the hippocampus

Rats, implanted with dialysis loops in the dorsal hippocampus, were injected with subconvulsant doses of pentylenetetrazole (PTZ 15 and 30 mg/kg) and a 30-min sample collected for high-performance liquid chromatography (HPLC) analysis of amines and amino acids. Immediately after the sampling period they were given a 5-min test in the elevated plus-maze. On the basis of their performance in this test, they were divided into an 'anxious' and a 'non-anxious' group. The anxious group had significantly lower levels of glycine and serotonin (5-HT) release. Although PTZ decreased the release of noradrenaline, this was not correlated with behavioural differences in the elevated plus-maze.     

Higher bioelectric potentials due to decreased chloride absorption in the sweat glands of patients with cystic fibrosis

Patients with cystic fibrosis have characteristic disturbances in the electrolyte composition of their sweat, saliva, and pancreatic secretions. We studied the electrical properties of sweat glands in eight patients with cystic fibrosis and in seven normal volunteers to determine the basis of the well-documented inhibition of sodium absorption in this disease. The average electrical potential across 47 sweat glands in the patients was -66.3 +/- 2.1 mV, as compared with -29.8 +/- 3.2 mV for 39 glands in the normal controls (P less than 0.001). The average sweat-secretion rate in 33 glands from six patients was not significantly different from that in 34 glands from six controls, but average concentrations of sodium, chloride, and potassium were significantly higher in sweat droplets from the patients. Calculated rates of both sodium and chloride reabsorption were lower in sweat glands of patients than of normal controls, but chloride reabsorption was more markedly reduced than sodium reabsorption. We conclude that a decrease in epithelial permeability to chloride may explain the characteristic changes in sweat electrolytes in cystic fibrosis and could be a generalized abnormality in the disease.     

False-positive culture results from patient tissue specimens due to contamination of RPMI medium with Cryptococcus albidus

Cryptococcus albidus, a rare opportunist, was isolated from biopsy specimens from three patients over 4 days. An investigation showed that the specimens had been contaminated by placement in RPMI medium. The importance of rapid communication between the microbiology laboratory, the infectious diseases/infection control division, and other involved parties in the event of unusual occurrences is highlighted.