Retinal and renal complications in patients with a mutation of mitochondrial DNA at position 3,243 (maternally inherited diabetes and deafness). A case–control study

AIMS/HYPOTHESIS: We assessed the prevalence and determinants of retinal and renal complications in patients with maternally inherited diabetes and deafness (MIDD). METHODS: This was a multicentre prospective study comparing the prevalence of retinopathy and renal disease in 74 patients with MIDD and 134 control patients matched for sex, age and clinical presentation at onset of diabetes, duration of diabetes and current treatment. Comparisons were adjusted for HbA(1c) and hypertension. RESULTS: In MIDD patients, HbA(1c) (7.6 +/- 1.6 vs 8.5 +/- 2.0%, p < 0.002), systolic blood pressure (126.6 +/- 16.2 vs 133.1 +/- 17.3 mmHg, p < 0.007) and prevalence of hypertension (33.8 vs 64.2%, p < 0.0001) were lower than in control patients. Prevalence of diabetic retinopathy was 3.7-fold lower in MIDD patients (6/74, 8 vs 40/134, 29.6%, p < 0.0001). Differences between groups remained significant after adjustment for hypertension, systolic blood pressure and HbA(1c). In MIDD, urinary albumin excretion (314.8 vs 80.1 mg/24 h, p = 0.035) and creatinine plasma levels (103.5 vs 82.2 micromol/l, p = 0.0178) were higher and GFR was lower. Impaired renal function (GFR <60 ml/min) was four- to sixfold more frequent in MIDD. Differences between MIDD and control diabetic patients further increased when adjusted for HbA(1c) and systolic blood pressure (p < 0.0001). Adjustment for treatment with an ACE inhibitor or angiotensin II receptor antagonist did not modify the results. CONCLUSIONS/INTERPRETATION: This study indicates that diabetic retinopathy is less prevalent in MIDD than in control diabetes. This suggests that retinal alterations due to mitochondrial disease may have a protective role. By contrast, nephropathy is far more frequent in MIDD, suggesting the presence of a specific renal disease independent of diabetic nephropathy.     

ROR1 is essential for proper innervation of auditory hair cells and hearing in humans and mice

Hair cells of the inner ear, the mechanosensory receptors, convert sound waves into neural signals that are passed to the brain via the auditory nerve. Little is known about the molecular mechanisms that govern the development of hair cell–neuronal connections. We ascertained a family with autosomal recessive deafness associated with a common cavity inner ear malformation and auditory neuropathy. Via whole-exome sequencing, we identified a variant (c.2207G>C, p.R736T) in ROR1 (receptor tyrosine kinase-like orphan receptor 1), cosegregating with deafness in the family and absent in ethnicity-matched controls. ROR1 is a tyrosine kinase-like receptor localized at the plasma membrane. At the cellular level, the mutation prevents the protein from reaching the cellular membrane. In the presence of WNT5A, a known ROR1 ligand, the mutated ROR1 fails to activate NF-κB. Ror1 is expressed in the inner ear during development at embryonic and postnatal stages. We demonstrate that Ror1 mutant mice are severely deaf, with preserved otoacoustic emissions. Anatomically, mutant mice display malformed cochleae. Axons of spiral ganglion neurons show fasciculation defects. Type I neurons show impaired synapses with inner hair cells, and type II neurons display aberrant projections through the cochlear sensory epithelium. We conclude that Ror1 is crucial for spiral ganglion neurons to innervate auditory hair cells. Impairment of ROR1 function largely affects development of the inner ear and hearing in humans and mice.Sensorineural hearing loss (SNHL) is diagnosed in approximately 1 per 500 newborns (1). A genetic etiology is present in more than half of the cases. Inner ear anomalies (IEAs), demonstrated with computerized tomography or magnetic resonance imaging, are associated with SNHL in about one-third of individuals (2). Although IEAs can be diagnosed in patients with other clinical manifestations, such as those seen in Waardenburg [Mendelian Inheritance in Man (MIM) 193500], Pendred (MIM 274600), or BOR (MIM 113650) syndromes, the majority of cases fall into the category of nonsyndromic deafness. Despite recent progress in identifying genes that determine many forms of hearing loss (hereditaryhearingloss.org/), the genetic basis of IEAs in humans remains largely unknown.The inner ear is a complex organ that is built from a simple structure, referred to as the otocyst, through a series of morphogenetic events. Roughly, it consists of a dorsal vestibular and a ventral auditory component (3). Studies in model organisms have identified a number of genes that play roles in proper development of the inner ear. Mouse models have been particularly relevant because the anatomy and physiology of the murine auditory system are similar to those of humans. Mutations in human orthologs of many of these genes have been reported to cause deafness in humans as well (4).Next-generation sequencing technologies have allowed rapid identification of novel human deafness genes. Approximately 85% of disease-causing mutations in Mendelian disorders have been found in the protein-coding regions, despite the fact that this portion accounts for less than 2% of the entire human genome (5). Accordingly, whole exome sequencing (WES) has been frequently used because it allows for a targeted enrichment and resequencing of nearly all exons of protein-coding genes.In this study, via WES, we detected a mutation in ROR1 (receptor tyrosine kinase-like orphan receptor 1; MIM 602336), encoding receptor tyrosine kinase-like orphan receptor 1, that associates with an IEA and nonsyndromic deafness in a family. Further characterization of Ror1 mutant mice revealed that Ror1 deficiency results in defective hair cell innervation and abnormal cochlear development.     

A Novel De Novo GATA Binding Protein 3 Mutation in a Turkish Boy with Hypoparathyroidism,Deafness, and Renal Dysplasia Syndrome

Hypoparathyroidism, deafness, and renal dysplasia (HDR; OMIM 146255) syndrome is a rare disease, inherited dominantly and found to be related with GATA3 (GATA binding protein 3) gene mutations. A 13-year and 8-month-old boy who presented with hypocalcemia was diagnosed with hypoparathyroidism. He also had dysmorphic facial features, renal anomaly (pelvic kidney), and mild sensorineural hearing loss. His cranial computed tomography revealed multiple calcifications in bilateral centrum semiovale, corona radiata, and basal ganglions suggesting a persistent hypoparathyroidism. Thus, the presence of triad of HDR syndrome was considered, and genetic analysis using a next-generation sequencer identified a novel de novo missense mutation in exon 4 p.R276Q (c.827G>A) of GATA3 gene. This is the second patient who was reported to have a mutation in GATA3 gene from Turkey. In conclusion, although HDR syndrome is a rare condition, it should be kept in mind in patients with hypoparathyroidism. Classical triad can easily be identified if patients diagnosed with hypoparathyroidism are also evaluated with a urinary tract ultrasound and an audiometer.     

Spontaneous regeneration of cochlear supporting cells after neonatal ablation ensures hearing in the adult mouse

Supporting cells in the cochlea play critical roles in the development, maintenance, and function of sensory hair cells and auditory neurons. Although the loss of hair cells or auditory neurons results in sensorineural hearing loss, the consequence of supporting cell loss on auditory function is largely unknown. In this study, we specifically ablated inner border cells (IBCs) and inner phalangeal cells (IPhCs), the two types of supporting cells surrounding inner hair cells (IHCs) in mice in vivo. We demonstrate that the organ of Corti has the intrinsic capacity to replenish IBCs/IPhCs effectively during early postnatal development. Repopulation depends on the presence of hair cells and cells within the greater epithelial ridge and is independent of cell proliferation. This plastic response in the neonatal cochlea preserves neuronal survival, afferent innervation, and hearing sensitivity in adult mice. In contrast, the capacity for IBC/IPhC regeneration is lost in the mature organ of Corti, and consequently IHC survival and hearing sensitivity are impaired significantly, demonstrating that there is a critical period for the regeneration of cochlear supporting cells. Our findings indicate that the quiescent neonatal organ of Corti can replenish specific supporting cells completely after loss in vivo to guarantee mature hearing function.Inner hair cells (IHCs), the sensory cells of the mammalian auditory sensory epithelium, are surrounded by specialized supporting cells (SCs) called “inner border cells” (IBCs) and “inner phalangeal cells” (IPhCs) (Fig. S1A). IBCs and IPhCs, together with other SCs, are known to play critical roles during the development and maturation of the organ of Corti, in processes such as patterning of the epithelium, synaptogenesis, and initiation of electrical activity in auditory nerves before the onset of hearing and formation of extracellular matrices (1–7). SCs also are essential for the function of the mature organ of Corti, where they contribute to the maintenance of the reticular lamina at the apical surface of the epithelium (8), control the extracellular concentration of ions (e.g., K⁺) (9, 10) and neurotransmitters (e.g., glutamate) (11), and support hair cell (HC) and auditory sensory neuron survival (5, 12–15). SCs also have been proposed to regulate the effects of insults on HCs by releasing molecules that either promote (e.g., ERK1 and 2) (16) or reduce (e.g., heat shock protein 70) (17) HC death. Additionally, SCs impact the extent of damage in the auditory epithelium through scar formation and clearance of HC debris (18). Furthermore, SCs are considered a potential source of cells for HC replacement in mammals, because SCs are a documented source of new HCs in cultured neonatal cochlea (19) and in adult utricles (20). Additionally, nonmammalian vertebrates regenerate HCs and SCs after damage and recover hearing, with the SCs being the source of the regenerative response (21–23). Indeed, if SCs are damaged by insults, the regenerative response is severely compromised (1, 24). Thus, it is assumed that the presence of these cells in the postnatal cochlea is essential for hearing, but specific roles of IBCs and IPhCs in HC maintenance and cochlear function have not been established.To determine the consequences of neonatal IBC and IPhC loss on the mature organ of Corti, we ablated these cells in vivo using an inducible diphtheria toxin fragment A (DTA) transgenic approach (25). Unexpectedly, we found that when these IHC supporting cells are eliminated immediately after birth, they are replaced efficiently within days. Moreover, this regeneration preserves the structure and function of the organ of Corti, so that mice with transient IBC/IPhC loss retain normal hearing as adults. In contrast, IBCs and IPhCs do not regenerate if ablation occurs after the onset of hearing, resulting in IHC loss and severe hearing impairment. Our studies also indicate that IBC and IPhC replacement in the neonatal cochlea results from transdifferentiation of less-specified SCs within the neighboring greater epithelial ridge (GER or Kölliker’s organ), which does not require cell proliferation. The unexpected regenerative capacity of SCs in the early postnatal organ of Corti in vivo may provide new strategies to regenerate its nonsensory and sensory cells after damage.     

突发性耳聋患者耳鸣状况的危险因素研究

目的探讨突发性耳聋患者耳鸣状况的危险因素。方法收集2006年1月—2012年12月该院收治的507例突发性耳聋患者完整的病历资料,对其听力损失的程度、听力曲线的类型及治疗效果进行评定,对耳鸣响度进行分级。分析不同耳鸣程度的相关影响因素。结果 507例突发性耳聋伴耳鸣患者的耳鸣程度以3级所占的比例最大,为32.94%（167/507）;所占比例最低的为1级,为13.02%（66/507）;2、4级分别各占27.02%（137/507）。不同耳鸣程度的患者在年龄、性别、耳侧、不同听力损害程度及不同听力曲线类型等方面的分布情况相比,均无统计学差异（P〉0.05）。结论患者在年龄、性别、耳侧等方面的不同分布情况、不同听力损害程度及不同听力曲线类型等不同的突发性耳聋的听力学特征及治疗效果与耳鸣的严重程度并不存在相关性,并非造成突发性耳聋患者伴发不同严重程度耳鸣的独立的危险因素。     

Identification of Three Novel and One Known Mutation in the WFS1 Gene in Four Unrelated Turkish Families: The Role of Homozygosity Mapping in the Early Diagnosis

Objective:Bi-allelic mutations in the wolframin gene (WFS1) cause Wolfram syndrome 1 (WS1 or DIDMOAD) characterized by non-autoimmune diabetes mellitus, optic atrophy, diabetes insipidus, sensorineural deafness, urinary tract abnormalities, and neuropsychiatric disorders. Patients presenting with an incomplete phenotype of WS1 were evaluated using homozygosity mapping and subsequent whole-exome sequencing.Methods:Four unrelated consanguineous Turkish families, including seven affected children, and their unaffected parents and siblings were evaluated. Homozygosity mapping was performed, followed by whole-exome sequencing of WFS1. Mutations were classified according to results of “in silico” analyses, protein prediction, and functional consequences.Results:Homozygosity mapping confirmed shared homozygous regions on chromosome 4 (chr4p16.1) between the affected individuals, that was absent in their unaffected siblings. Exome sequencing identified three novel (c.1215T>A, c.554G>A, c.1525_1540dup) and one known (c.1522_1523delTA) mutations in WFS1. All mutations were predicted to cause stop codon leading to early termination of protein synthesis and complete loss-of-function. All patients were found to be homozygous for the change, with parents and other unaffected siblings being carriers.Conclusion:Our study expands the mutation spectrum of WSF1 mutations with three novel mutations. Homozygosity mapping may provide enrichment for molecular genetic analysis and early diagnosis of WS1 patients with incomplete phenotype, particularly in consanguineous pedigrees.     

缪刺对突发性耳聋临床及TCD的影响

目的：观察缪刺治疗突发性耳聋的疗效及对经颅多普勒（TCD）脑血流参数的影响。方法：选择突发性耳聋病例,随机分为治疗组及对照组各50例,两组患者均采用常规综合治疗,治疗组在此基础上加用缪刺治疗及针刺治疗,治疗前后观察疗效并检测经颅多普勒（TCD）脑血流参数。结果：治疗组疗效明显,与对照组相比差异有显著性（P〈0．01）;治疗组治疗后TCD脑血流参数不同程度地改善,与组内治疗前比较差异有显著性意义（P〈0．01）,与对照组治疗后比较差异亦有显著性（P〈0．01）。结论：缪刺治疗突发性耳聋较常规治疗疗效好,并可改善突聋患者经颅多普勒（TCD）脑血流参数,进行TCD检测可反映突聋患者内耳及脑干的供血状况,对指导临床治疗及评价预后有重要意义。     

Otolaryngological manifestations of ‘Muckle-Wells syndrome’

We present a follow-up of a cohort of three cases of Muckle-Wells syndrome (MWS). The aim of this report is to characterise the symptoms of this rare autosomal dominant condition with respect to the ENT practice. A retrospective analysis of the clinical features of MWS from our outpatient follow-up record of the three patients diagnosed with MWS. An extensive literature search was performed, using Medline through Pub Med (1950-2010), EMBASE (1980-2009) and Ovid (1958-2009). Retrospective case note study. In the present cohort, progressive sensorineural hearing loss was the main presentation and has been followed up over 10 years (median). The spectrum of head and neck presentation from the world literature was reviewed and includes hypothyroidism, amyloid goitre, cervical lymphadenopathy, and facial rash. This is the first documented report of the Otolaryngological features of the MWS in the English ENT literature. An awareness of this rare syndrome is essential in order to diagnose this uncommon syndrome and thus to plan for a long-term follow-up.     

Keratitis–ichthyosis–deafness syndrome accompanied by disseminated cutaneous fungal infection

Keratitis–ichthyosis–deafness (KID) syndrome is a rare genodermatosis. It is mostly associated with mutations of the connexin 26 gene, resulting in keratitis, erythrokeratoderma and neurosensory deafness. In addition to the clinical triad, the KID syndrome patients are at high risk for infectious complications, while the mechanisms are poorly understood. In the present article, we described an Asian case of KID syndrome accompanied by fungal infection. The present study was designed to define the mutation type, and further to explore the interaction between the innate immunity response and the infectious complication of KID syndrome. Genomic DNA was extracted from peripheral blood for mutation analysis. Isolation and identification of the species were carried out to confirm the infectious microorganism. Three biopsy specimens from different parts of the body (right thigh, abdomen and forehead, respectively) were carried out for histopathological and immunohistochemical analysis. Furthermore, quantitative polymerase chain reaction (PCR) was carried out to study the expression of Toll‐like receptor 2 (TLR2) on the epidermis of the right thigh. We identified a mutation (p.G12R) in the GJB2 gene in this patient with Trichophyton rubrum infection. Immunohistochemistry staining revealed a lower expression of TLR2 and no significant difference in TLR4. Meanwhile, PCR showed a relatively slight increase of TLR2 RNA expression. These results indicated that GJB2 mutation (p.G12R) in this case of KID syndrome, which was susceptible to T. rubrum infection, might be attributed to a limited native immune response.     

Germline mosaicism in keratitis–ichthyosis–deafness syndrome: pre‐natal diagnosis in a familial lethal form

Sbidian E, Feldmann D, Bengoa J, Fraitag S, Abadie V, de Prost Y, Bodemer C, Hadj‐Rabia S. Germline mosaicism in keratitis–ichthyosis–deafness syndrome: pre‐natal diagnosis in a familial lethal form. Keratitis–ichthyosis–deafness (KID) syndrome is an autosomal dominant congenital ectodermal defect characterized by the association of skin lesions, hearing loss and keratitis. Most of the cases appear to be sporadic. KID syndrome is mostly related to mutations of GJB2 gene encoding connexin‐26. Recently, a lethal form of the disease during the first year of life has been reported in two unrelated Caucasian patients. This rare lethal form is caused by the G45E mutation of GJB2 gene. We here report the first pre‐natal molecular genetic diagnosis of the lethal form of KID syndrome relating to a G45E mutation. In the same family, the occurrence of this condition in three other siblings born to African non‐consanguineous healthy parents lead to perform pre‐natal diagnosis for this last pregnancy. Molecular analysis confirms the diagnosis of the lethal form of KID for the fetus. These results establish the role of germline mosaicism in KID syndrome and warrant careful genetic counseling. Furthermore, analysis of our cases and the literature allowed us to define a characteristic severe neonatal phenotype including facial dysmorphy, severe cornification with massive focal hyperkeratosis of the skin with erythroderma, dystrophic nails, complete atrichia and absence of foreskin.