New variant of familial cerebellar ataxia with hypergonadotropic hypogonadism and sensorineural deafness

The Bacterial ClpXP-ClpB Family Is Enriched with RNA-Binding Protein Complexes

In the matrix of bacteria/mitochondria/chloroplasts, Lon acts as the degradation machine for soluble proteins. In stress periods, however, proteostasis and survival depend on the strongly conserved Clp/Hsp100 family. Currently, the targets of ATP-powered unfoldases/disaggregases ClpB and ClpX and of peptidase ClpP heptameric rings are still unclear. Trapping experiments and proteome profiling in multiple organisms triggered confusion, so we analyzed the consistency of ClpP-trap targets in bacteria. We also provide meta-analyses of protein interactions in humans, to elucidate where Clp family members are enriched. Furthermore, meta-analyses of mouse complexomics are provided. Genotype–phenotype correlations confirmed our concept. Trapping, proteome, and complexome data retrieved consistent coaccumulation of CLPXP with GFM1 and TUFM orthologs. CLPX shows broad interaction selectivity encompassing mitochondrial translation elongation, RNA granules, and nucleoids. CLPB preferentially attaches to mitochondrial RNA granules and translation initiation components; CLPP is enriched with them all and associates with release/recycling factors. Mutations in CLPP cause Perrault syndrome, with phenotypes similar to defects in mtDNA/mtRNA. Thus, we propose that CLPB and CLPXP are crucial to counteract misfolded insoluble protein assemblies that contain nucleotides. This insight is relevant to improve ClpP-modulating drugs that block bacterial growth and for the treatment of human infertility, deafness, and neurodegeneration.

Biallelic SQSTM1 mutations in early-onset, variably progressive neurodegeneration

OBJECTIVE

To characterize clinically and molecularly an early-onset, variably progressive neurodegenerative disorder characterized by a cerebellar syndrome with severe ataxia, gaze palsy, dyskinesia, dystonia, and cognitive decline affecting 11 individuals from 3 consanguineous families.

METHODS

We used whole-exome sequencing (WES) (families 1 and 2) and a combined approach based on homozygosity mapping and WES (family 3). We performed in vitro studies to explore the effect of the nontruncating SQSTM1 mutation on protein function and the effect of impaired SQSTM1 function on autophagy. We analyzed the consequences of sqstm1 down-modulation on the structural integrity of the cerebellum in vivo using zebrafish as a model.

RESULTS

We identified 3 homozygous inactivating variants, including a splice site substitution (c.301+2T>A) causing aberrant transcript processing and accelerated degradation of a resulting protein lacking exon 2, as well as 2 truncating changes (c.875_876insT and c.934_936delinsTGA). We show that loss of SQSTM1 causes impaired production of ubiquitin-positive protein aggregates in response to misfolded protein stress and decelerated autophagic flux. The consequences of sqstm1 down-modulation on the structural integrity of the cerebellum in zebrafish documented a variable but reproducible phenotype characterized by cerebellum anomalies ranging from depletion of axonal connections to complete atrophy. We provide a detailed clinical characterization of the disorder; the natural history is reported for 2 siblings who have been followed up for >20 years.

CONCLUSIONS

This study offers an accurate clinical characterization of this recently recognized neurodegenerative disorder caused by biallelic inactivating mutations in SQSTM1 and links this phenotype to defective selective autophagy.

Heterozygous mutations in HSD17B4 cause juvenile peroxisomal D-bifunctional protein deficiency

Objective:

To determine the genetic cause of slowly progressive cerebellar ataxia, sensorineural deafness, and hypergonadotropic hypogonadism in 5 patients from 3 different families.

Methods:

The patients comprised 2 sib pairs and 1 sporadic patient. Clinical assessment included history, physical examination, and brain MRI. Linkage analysis was performed separately on the 2 sets of sib pairs using single nucleotide polymorphism microarrays, followed by analysis of the intersection of the regions. Exome sequencing was performed on 1 affected patient with variant filtering and prioritization undertaken using these intersected regions.

Results:

Using a combination of sequencing technologies, we identified compound heterozygous mutations in HSD17B4 in all 5 affected patients. In all 3 families, peroxisomal D-bifunctional protein (DBP) deficiency was caused by compound heterozygosity for 1 nonsense/deletion mutation and 1 missense mutation.

Conclusions:

We describe 5 patients with juvenile DBP deficiency from 3 different families, bringing the total number of reported patients to 14, from 8 families. This report broadens and consolidates the phenotype associated with juvenile DBP deficiency.

An Application of NGS for Molecular Investigations in Perrault Syndrome: Study of 14 Families and Review of the Literature

Perrault syndrome (PS) is a rare autosomal recessive condition characterized by deafness and gonadic dysgenesis. Recently, mutations in five genes have been identified: C10orf2, CLPP, HARS2, HSD17B4, and LARS2. Probands included are presented with sensorineural deafness associated with gonadic dysgenesis. DNA was sequenced using next-generation sequencing (NGS) with a panel of 35 deafness genes including the five Perrault genes. Exonic variations known as pathogenic mutations or detected with <1% frequency in public databases were extracted and subjected to segregation analysis within each family. Both mutations and low coverage regions were analyzed by Sanger sequencing. Fourteen female index patients were included. The screening in four cases has been extended to four family members presenting with PS phenotype. For four unrelated patients (28.6%), causative mutations were identified: three homozygous mutations in C10orf2, CLPP, and HARS2, and one compound heterozygous mutation in LARS2. Three additional heterozygous mutations in LARS2 and HSD17B4 were found in three independent familial cases. All these missense mutations were verified by Sanger sequencing. Familial segregation analyses confirmed the molecular diagnosis in all cases carrying biallelic mutations. Because of NGS, molecular analysis confirmed the clinical diagnosis of PS in 28.6% of our cohort and four novel mutations were found in four Perrault genes. For the unsolved cases, exome sequencing should be performed to search for a sixth unknown PS gene.

Genetics of female infertility due to anomalies of the ovary and mullerian ducts

Genetic factors are pivotal in reproductive development and subsequent reproductive processes. If disturbed, infertility can occur. In the female, genetic factors affecting the ovary and the uterus are not uncommon causes of infertility. Terminal deletions on the X long arm and X short arm and X chromosomal mosaicism have long been accepted as causes of premature ovarian failure (POF). Responsible genes on the X have not yet elucidated. Attractive candidate genes for POF also exist on autosomes, and in over a dozen genes molecular perturbations are documented in non-syndromic POF. The most common single-gene cause of POF is premutation carriers for FMR1 (fragile X syndrome). As other candidate genes and additional ethnic groups are interrogated, the proportion of POF cases due to single-gene mutation will increase. Among uterine anomalies, incomplete mullerian fusion is most common. Increased recurrence risks for first-degree relatives confirm a role for genetic factors; interrogation of candidate genes is under way.

Severe manifestation of Leber's hereditary optic neuropathy due to 11778G>A mtDNA mutation in a female with hypoestrogenism due to Perrault syndrome

Perrault syndrome (PS) is a rare autosomal recessive condition with ovarian dysgenesis, hearing deficit and neurological abnormalities in female patients. The molecular basis of the syndrome is heterogeneous, mutations in the HSD17B4 gene have been identified in one family and mutations in the HARS2 gene have been found in another one. We have excluded pathogenic changes in the HSD17B4 gene and in the HARS2 gene by a direct sequencing of all coding exons in a female with clinical hallmarks of PS, ataxia and mild mental retardation. In addition, the patient suffers from severe Leber's hereditary optic neuropathy (LHON) due to 11778G>A mtDNA mutation. This case is the first reported patient with PS and LHON. Possible influence of hypoestrogenism on the manifestation of optic neuropathy in this patient is discussed in the context of recent findings concerning the crucial role of estrogens in supporting the vision capacity in LHON-related mtDNA mutation carriers.

Other autosomal recessive and childhood ataxias

The label of "early-onset cerebellar ataxia with retained tendon reflexes" (EOCA) has been created to differentiate it from Friedreich ataxia (FRDA) patients with preserved knee jerks and absence of cardiomyopathy, optic atrophy, and diabetes mellitus. However, EOCA is a heterogeneous syndrome and several FRDA patients present with an EOCA-like phenotype. Cerebellar ataxia with hypogonadism is another heterogeneous syndrome for which no locus has been mapped yet. Two peculiar ataxic syndromes have been identified in genetically isolated populations: autosomal recessive ataxia of Charlevoix-Saguenay (ARSACS) in Quebec and infantile-onset spinocerebellar ataxia (IOSCA) in Finland. Both conditions present usually within the second year of life. ARSACS is characterized by marked spasticity and IOSCA by a complex phenotype which includes, besides ataxia, epilepsy, optic atrophy, ophthalmoplegia, hearing loss, and areflexia. The responsible genes are SACS, encoding sacsin, a protein which may act as a chaperone, and C10orf2, encoding Twinkle, a mitochondrial DNA-specific helicase. Marinesco-Sjögren syndrome, clinically characterized by cerebellar ataxia, cataracts, myopathy, and mental retardation, is genetically heterogeneous. One gene, SIL1, encodes a nucleotide exchange factor for the heat-shock protein 70 chaperone HSPA5. Five conditions account for most cases of progressive myoclonic ataxia: Unverricht-Lundborg disease, Lafora disease, myoclonic epilepsy with ragged-red fibers, neuronal ceroid lipofuscinoses, and sialidoses.

Hypergonadotropic hypogonadism, progressive early-onset spinocerebellar ataxia, and late-onset sensorineural hearing loss: case report and literature review

The association of ataxia, hypergonadotropic hypogonadism and hearing loss is extremely rare. Considerable heterogeneity exists in the literature of the neurological manifestations, age of onset, clinical severity and associated abnormalities. We describe a 24-year-old woman with secondary hypergonadotropic amenorrhea, early-onset progressive spinocerebellar ataxia (SCA), late-onset sensorineural hearing loss and normal intelligence and compare it with reported cases.

Mutations in mitochondrial histidyl tRNA synthetase HARS2 cause ovarian dysgenesis and sensorineural hearing loss of Perrault syndrome

Perrault syndrome is a genetically heterogeneous recessive disorder characterized by ovarian dysgenesis and sensorineural hearing loss. In a nonconsanguineous family with five affected siblings, linkage analysis and genomic sequencing revealed the genetic basis of Perrault syndrome to be compound heterozygosity for mutations in the mitochondrial histidyl tRNA synthetase HARS2 at two highly conserved amino acids, L200V and V368L. The nucleotide substitution creating HARS2 p.L200V also created an alternate splice leading to deletion of 12 codons from the HARS2 message. Affected family members thus carried three mutant HARS2 transcripts. Aminoacylation activity of HARS2 p.V368L and HARS2 p.L200V was reduced and the deletion mutant was not stably expressed in mammalian mitochondria. In yeast, lethality of deletion of the single essential histydyl tRNA synthetase HTS1 was fully rescued by wild-type HTS1 and by HTS1 p.L198V (orthologous to HARS2 p.L200V), partially rescued by HTS1 p.V381L (orthologous to HARS2 p.V368L), and not rescued by the deletion mutant. In Caenorhabditis elegans, reduced expression by RNAi of the single essential histydyl tRNA synthetase hars-1 severely compromised fertility. Together, these data suggest that Perrault syndrome in this family was caused by reduction of HARS2 activity. These results implicate aberrations of mitochondrial translation in mammalian gonadal dysgenesis. More generally, the relationship between HARS2 and Perrault syndrome illustrates how causality may be demonstrated for extremely rare inherited mutations in essential, highly conserved genes.

[A woman with cerebellar ataxia and hypergonadotropic hypogonadism]

A 26-year-old woman with primary amenorrhea in association with hypergonadotropinism, and lacking a vagina and uterus, suffered from a gradually progressive gait disturbance in her adolescence. The patient has no family history of ataxia and a chromosome study showed a normal karyotype (46,XX). Using the revised Hasegawa Dementia Scale, her cognitive function was measured as that of a normal adult, however, neurological examination revealed symptoms of scanning speech, horizontal gaze-evoked nystagmus, and ataxia. Bulging eyes, high-arched palate, scoliosis and ventricular septal defect were also observed. A brain MRI showed atrophy of the cerebellum. A 123I-IMP brain SPECT study showed hypoperfusion in the cerebellum. Previous studies show that among patients with cerebellar ataxia and hypergonadotropic hypogonadism, some show an autosomal recessive inheritance, while others have no family history. As a cause, a chromosomal abnormality is unlikely because all reported karyotypes were normal. This case is different from other reported cases in that she is not mentally impaired or deaf. The present case indicates that there is a close relationship between cerebellar ataxia and hypogonadism, and that other symptoms such as deafness and mental impairment could be an additional variable in patients with cerebellar ataxia arid hypergonadotropic hypogonadism.

Sensorimotor neuronopathy in ataxia with oculomotor apraxia type 2

Two siblings with ataxia with oculomotor apraxia type 2 (AOA2) exhibited electrophysiological findings suggestive of a sensorimotor neuronopathy, and primary ovarian failure was detected in one of them. Genetic analysis disclosed a novel, homozygous frameshift mutation in the senataxin gene, 2755_2756delGT, responsible for a premature stop codon at position 2760. It is suggested that a neuronopathy might cause the neuromuscular disturbance in AOA2, and that ovarian failure should be looked for in female patients with the disease.

Hypergonadotropic hypogonadism in spinocerebellar ataxia type 2: a case report

INTRODUCTION

The association between cerebellar ataxia and hypogonadism is seen rarely and is not well recognized. Spinocerebellar ataxia (SCA) is an autosomal dominantly inherited, progressive ataxia disorder, and SCA type 2 (SCA2) characteristically presents with a highly variable phenotype with multisystemic involvement. Although the clinical spectrum of SCA2 is broad, hypogonadism has not been reported as an accompanying symptom.

AIM

To report a case study that describes hypergonadotropic hypogonadism as a non-neurological manifestation of cerebellar ataxia in a patient with a hereditary trinucleotide repeat expansion disorder, SCA2.

METHODS

Case report of a man admitted to an academic medical center.

RESULTS

A 45-year-old man with a history of azoospermia in work-up for infertility was admitted for evaluation of a left-side hand tremor, instability on walking and impaired balance. Upon physical examination, the patient had a micropenis about 3 cm in length and had decreased testicular size (12 cc each) on orchidometry, but normal secondary sexual characteristics and average stature. Laboratory tests showed the presence of hypergonadotropic hypogonadism. A brain magnetic resonance imaging scan showed marked atrophy involving both the cerebellum and pons. Genetic analysis for hereditary ataxia demonstrated the presence of a 37 CAG triplet expansion in the mutated allele (genotype 22/37) in the SCA2 gene, confirming the diagnosis of SCA2.

CONCLUSION

The present study suggests that a common genetic implication may be shared between these neurologic and non-neurologic signs, and there may be various associations between these heterogeneous manifestations. The clinical spectrum of the SCA2 should be widened, and further data collection is needed to elucidate the relationship among the clinical manifestations.

Ovarian failure in ataxia with oculomotor apraxia type 2

Ataxia with oculomotor apraxia type 2 (AOA2) is an autosomal recessive disorder associated with mutations in the Senataxin (SETX) gene. Clinical manifestations (ataxia, peripheral neuropathy, oculomotor apraxia) of this disease have previously been limited to the nervous system. We describe a patient homozygous for a novel mutation of SETX who manifested not only ataxia but also ovarian failure.

[Gonadal dysgenesis and tumors: genetic and clinical features]

Gonadal dysgenesis comprises a clinical spectrum of anomalies in patients with female, ambiguous or male phenotype, absent or impaired puberty and karyotype with or without Y chromosome and/or chromosome markers. Although Y-specific sequences are seldom cytogenetically evident, dysgenetic gonads are potentially prone to developing tumors. Gonadoblastoma, a mixed germ cell and sex-cord cells tumor with variable degree of focal calcification, is the most harmful due to its frequency. Other gonadal tumor, malign or not, also occur in gonadal dysgenesis. As they are not metastatic tumors and may be eradicated by selective excisions, the importance of detecting Y-sequences by molecular sensitized techniques is stressed in order to indicate prophylactic gonadectomy.

Spinocerebellar ataxia and hypergonadotropic hypogonadism associated with familial sensorineural hearing loss

Cerebellar ataxia has been described as being associated with hypogonadism for almost 100 years. In the majority of cases, hypogonadism is hypogonadotropic. The association of cerebellar ataxia with hypergonadotropic hypogonadism is a rare genetic disorder with a recessive mode of inheritance. Cerebellar ataxia and hypogonadism can also occur associated with a large spectrum of additional clinical manfestations, including mental retardation, sensorineural deafness, choroidal dystrophy, ectodermal dysplasia and short stature, and polyneuropathy. We report the case of a woman with early-onset spinocerebellar ataxia, primary amenorrhea due to hypergonadotropic hypogonadism, and late-onset sensorineural hearing loss. Additional family members from the father's side are affected with late-onset hearing loss, suggesting a dominant mode of inheritance.

Characterization of early presentation idiopathic ovarian failure in girls and adolescents

This study focused retrospectively on a selected cohort of 20 adolescents with early onset premature ovarian failure (POF) and no apparent underlying cause, in order to characterize the idiopathic ovarian failure at pediatric age. This characterization was based on medical history, pedigree analysis, phenotypical and audiological evaluation, final and target heights, pelvic ultrasonography, endocrine assessment, routine hematochemical analyses and complete autoimmune screening. We found that: a) idiopathic POF presented either before or after puberty onset and also with secondary amenorrhea; b) final height prognosis was impaired only in patients with prepubertal presentation of POF; c) ovarian pattern at ultrasonography and endocrine picture were similar those previously reported in patients with adult onset POF; d) clinical history and pedigree analysis, phenotypical and audiological examination and complete autoimmune screening failed to highlight the existence of any possible cause for POF in 15/20 patients; e) no alterations of total cholesterol, low-density lipoprotein cholesterol and high-density lipoprotein cholesterol serum levels were detected in any patient. On the basis of these results we concluded that: a) final height of the adolescents with POF may be impaired only in patients in whom POF presents as a pubertal delay; b) other parameters do not generally differ from those described by previous reports on young adults with POF, except for serum lipid levels which were normal in the present cohort.