Two case reports of a novel missense mutation in the PNPLA6 gene in two siblings with chorioretinal dystrophy, hypogonadotropic hypogonadism, and cerebellar ataxia.

BACKGROUND: Boucher Neuhäuser Syndrome (BNS) is a rare disease with autosomal recessive inheritance defined by the classical triad; early-onset ataxia, hypogonadism and chorioretinal dystrophy. CASE PRESENTATION: We present two siblings diagnosed with BNS at midlife, identified with homozygous state of a novel PNPLA6 missense mutation. One healthy sibling and the mother were heterozygous carriers of the mutation. The proband presented with the classical triad and the other sibling presented with visual problems at first. The proband was referred to our department by a private Neurologist, in early adulthood, because of hypogonadism, cerebellar ataxia, axonal neuropathy, and chorioretinal dystrophy for further evaluation. The sibling was referred to our department for evaluation, at childhood, due to visual problems. Later, the patient displayed the triad of ataxia, hypogonadotropic hypogonadism, and chorioretinal dystrophy. The unusual medical history of the two siblings led to further examinations and eventually the diagnosis of the first BNS cases in Cyprus. WES-based ataxia in silico gene panel analysis revealed 15 genetic variants and further filtering analysis revealed the PNPLA6 c.3323G > A variant. Segregation analysis in the family with Sanger sequencing confirmed the PNPLA6 homozygous variant c.3323G > A, p.Arg1108Gln in exon 29. CONCLUSIONS: This highlights the importance of considering rare inherited causes of visual loss, spinocerebellar ataxia, or/and HH in a neurology clinic and the significant role of genetic sequencing in the diagnostic process.

Spinal muscular atrophy type I associated with a novel SMN1 splicing variant that disrupts the expression of the functional transcript.

Introduction: Spinal muscular atrophy (SMA) is an autosomal recessive neuromuscular disorder caused by pathogenic variants in the SMN1 gene. The majority of SMA patients harbor a homozygous deletion of SMN1 exon 7 (95%). Heterozygosity for a conventional variant and a deletion is rare (5%) and not easily detected, due to the highly homologous SMN2 gene interference. SMN2 mainly produces a truncated non-functional protein (SMN-d7) instead of the full-length functional (SMN-FL). We hereby report a novel SMN1 splicing variant in an infant with severe SMA. Methods: MLPA was used for SMN1/2 exon dosage determination. Sanger sequencing approaches and long-range PCR were employed to search for an SMN1 variant. Conventional and improved Real-time PCR assays were developed for the qualitative and quantitative SMN1/2 RNA analysis. Results: The novel SMN1 splice-site variant c.835-8_835-5delinsG, was identified in compound heterozygosity with SMN1 exons 7/8 deletion. RNA studies revealed complete absence of SMN1 exon 7, thus confirming a disruptive effect of the variant on SMN1 splicing. No expression of the functional SMN1-FL transcript, remarkable expression of the SMN1-d7 and increased levels of the SMN2-FL/SMN2-d7 transcripts were observed. Discussion: We verified the occurrence of a non-deletion SMN1 variant and supported its pathogenicity, thus expanding the SMN1 variants spectrum. We discuss the updated SMA genetic findings in the Cypriot population, highlighting an increased percentage of intragenic variants compared to other populations.

The phenotypic spectrum of pathogenic ATP1A1 variants expands: the novel p.P600R substitution causes demyelinating Charcot-Marie-Tooth disease.

BACKGROUND: Charcot-Marie-Tooth disease (CMT) is a genetically and clinically heterogeneous group of inherited neuropathies. Monoallelic pathogenic variants in ATP1A1 were associated with axonal and intermediate CMT. ATP1A1 encodes for the catalytic α1 subunit of the Na+/ K+ ATPase. Besides neuropathy, other associated phenotypes are spastic paraplegia, intellectual disability, and renal hypomagnesemia. We hereby report the first demyelinating CMT case due to a novel ATP1A1 variant. METHODS: Whole-exome sequencing on the patient's genomic DNA and Sanger sequencing to validate and confirm the segregation of the identified p.P600R ATP1A1 variation were performed. To evaluate functional effects, blood-derived mRNA and protein levels of ATP1A1 and the auxiliary ß1 subunit encoded by ATP1B1 were investigated. The ouabain-survival assay was performed in transfected HEK cells to assess cell viability, and two-electrode voltage clamp studies were performed in Xenopus oocytes. RESULTS: The variant was absent in the local and global control datasets, falls within a highly conserved protein position, and is in a missense-constrained region. The expression levels of ATP1A1 and ATP1B1 were significantly reduced in the patient compared to healthy controls. Electrophysiology indicated that ATP1A1p.P600R injected Xenopus oocytes have reduced Na+/ K+ ATPase function. Moreover, HEK cells transfected with a construct encoding ATP1A1p.P600R harbouring variants that confers ouabain insensitivity displayed a significant decrease in cell viability after ouabain treatment compared to the wild type, further supporting the pathogenicity of this variant. CONCLUSION: Our results further confirm the causative role of ATP1A1 in peripheral neuropathy and broaden the mutational and phenotypic spectrum of ATP1A1-associated CMT.

Charcot-Marie-Tooth disease in Cyprus: epidemiological, clinical and genetic characteristics.

BACKGROUND: Charcot-Marie-Tooth disease (CMT) is the most common inherited neuropathy. CMT is classified into 2 main subgroups: a demyelinating and an axonal type. Further subdivisions within these 2 main categories exist and intermediate forms have more recently been described. Inheritance can be autosomal dominant, recessive or X-linked. CMT is associated with more than 30 loci, and about 25 causative genes have been described thus far. METHODS: We studied epidemiological, clinical and genetic characteristics of CMT in the Cypriot population. RESULTS: The prevalence of CMT in Cyprus on January 15, 2009, is estimated to be 16 per 100,000. Thirty-three families and 8 sporadic patients were ascertained. CMT was demyelinating in 52%, axonal in 33% and intermediate in 15% of the patients. Thirteen families had PMP22 duplication, 3 families had the PMP22 S22F mutation, 4 families had GJB1/Cx32 mutations, 2 families had different MPZ mutations, 1 of them novel, and 2 families had different MFN2 mutations. Nine families and 8 sporadic patients were excluded from the common CMT genes. CONCLUSION: The most frequent CMT mutation worldwide, the PMP22 duplication, is also the most frequent CMT mutation in the Cypriot population. Five out of the 8 other mutations are novel, not reported in other populations.

A novel c.5308_5311delGAGA mutation in Senataxin in a Cypriot family with an autosomal recessive cerebellar ataxia.

BACKGROUND: Senataxin (chromosome 9q34) was recently identified as the causative gene for an autosomal recessive form of Ataxia (ARCA), termed as Ataxia with Oculomotor Apraxia, type 2 (AOA2) and characterized by generalized incoordination, cerebellar atrophy, peripheral neuropathy, "oculomotor apraxia" and increased alpha-fetoprotein (AFP). Here, we report a novel Senataxin mutation in a Cypriot ARCA family. METHODS: We studied several Cypriot autosomal recessive cerebellar ataxia (ARCA) families for linkage to known ARCA gene loci. We linked one family (909) to the SETX locus on chromosome 9q34 and screened the proband for mutations by direct sequencing. RESULTS: Sequence analysis revealed a novel c.5308_5311delGAGA mutation in exon 11 of the SETX gene. The mutation has not been detected in 204 control chromosomes from the Cypriot population, the remaining Cypriot ARCA families and 37 Cypriot sporadic cerebellar ataxia patients. CONCLUSION: We identified a novel SETX homozygous c.5308_5311delGAGA mutation that co-segregates with ARCA with cerebellar atrophy and raised AFP.

Investigation of SCA10 in the Cypriot population: further exclusion of SCA dynamic repeat mutations.

Autosomal dominant cerebellar ataxias (ADCAs) encompass a heterogeneous group of rare diseases that affect the cerebellum and its connections. The most common forms have been associated with dynamic mutations while some rarer forms with conventional mutations. Studies in different populations revealed differences in their relative frequencies both within and between the studied populations, showing that the frequencies are depended on ethnic and geographical factors. Previous investigation of triplet repeat expansion SCAs (SCA1, SCA2, SCA3, SCA6, SCA7, SCA8, SCA12, SCA17 and DRPLA) in the Cypriot population, revealed no pathogenic expansion in the Cypriot SCA patients. We hereby present our recent investigation of the SCA10 pentanucleotide repeat expansion. Forty-two ascertained Cypriot sporadic ataxia patients, the index case from 1 ADCA and 14 ARCA families and a cohort of normal population individuals were included in the study. All our patients have normal range ATXN10 gene ATTCT repeat numbers (10-19). In the normal population group, repeat lengths ranged from 11 to 20 with the 14 repeats allele being the most frequent. Therefore, all currently established dynamic repeat SCA mutations are absent from the Cypriot population, indicating distinct genetic causes.

Complete deletion of the aprataxin gene: ataxia with oculomotor apraxia type 1 with severe phenotype and cognitive deficit.

Ataxia with oculomotor apraxia type 1 (AOA1) is a recently described autosomal-recessive neurodegenerative condition of childhood onset. It is caused by mutations in the APTX gene, which encodes the protein aprataxin. Clinical features include gait and limb ataxia, dysarthria, oculomotor apraxia, mild peripheral neuropathy and progression of neurological deficits.1 Some patients manifest parkinsonian symptoms or mental retardation, although the latter has been reported predominantly in Japanese patients.2 We report a patient with homozygous deletion of APTX, who presented with behavioural changes (social withdrawal), and subsequent rapid progression of neurological symptoms associated with severe cognitive decline. We suggest that complete deletion of APTX is associated with a more severe phenotype than that associated with point mutations.

The genomic sequence of the accidental pathogen Legionella pneumophila.

We present the genomic sequence of Legionella pneumophila, the bacterial agent of Legionnaires' disease, a potentially fatal pneumonia acquired from aerosolized contaminated fresh water. The genome includes a 45-kilobase pair element that can exist in chromosomal and episomal forms, selective expansions of important gene families, genes for unexpected metabolic pathways, and previously unknown candidate virulence determinants. We highlight the genes that may account for Legionella's ability to survive in protozoa, mammalian macrophages, and inhospitable environmental niches and that may define new therapeutic targets.