Clinical and neurogenetic characterisation of autosomal recessive RBL2-associated progressive neurodevelopmental disorder

Retinoblastoma (RB) proteins are highly conserved transcriptional regulators that play important roles during development by regulating cell-cycle gene expression. RBL2 dysfunction has been linked to a severe neurodevelopmental disorder. However, to date, clinical features have only been described in six individuals carrying five biallelic predicted loss of function (pLOF) variants. To define the phenotypic effects of RBL2 mutations in detail, we identified and clinically characterized a cohort of 28 patients from 18 families carrying LOF variants in RBL2 , including fourteen new variants that substantially broaden the molecular spectrum. The clinical presentation of affected individuals is characterized by a range of neurological and developmental abnormalities. Global developmental delay and intellectual disability were uniformly observed, ranging from moderate to profound and involving lack of acquisition of key motor and speech milestones in most patients. Frequent features included postnatal microcephaly, infantile hypotonia, aggressive behaviour, stereotypic movements and non-specific dysmorphic features. Common neuroimaging features were cerebral atrophy, white matter volume loss, corpus callosum hypoplasia and cerebellar atrophy. In parallel, we used the fruit fly, Drosophila melanogaster , to investigate how disruption of the conserved RBL2 orthologueue Rbf impacts nervous system function and development. We found that Drosophila Rbf LOF mutants recapitulate several features of patients harboring RBL2 variants, including alterations in the head and brain morphology reminiscent of microcephaly, and perturbed locomotor behaviour. Surprisingly, in addition to its known role in controlling tissue growth during development, we find that continued Rbf expression is also required in fully differentiated post-mitotic neurons for normal locomotion in Drosophila , and that adult-stage neuronal re-expression of Rbf is sufficient to rescue Rbf mutant locomotor defects. Taken together, this study provides a clinical and experimental basis to understand genotype-phenotype correlations in an RBL2 -linked neurodevelopmental disorder and suggests that restoring RBL2 expression through gene therapy approaches may ameliorate aspects of RBL2 LOF patient symptoms.

De novo heterozygous missense variants in CELSR1 as cause of fetal pleural effusions and progressive fetal hydrops

Fetal hydrops as detected by prenatal ultrasound usually carries a poor prognosis depending on the underlying aetiology. We describe the prenatal and postnatal clinical course of two unrelated female probands in whom de novo heterozygous missense variants in the planar cell polarity gene CELSR1 were detected using exome sequencing. Using several in vitro assays, we show that the CELSR1 p.(Cys1318Tyr) variant disrupted the subcellular localisation, affected cell-cell junction, impaired planar cell polarity signalling and lowered proliferation rate. These observations suggest that deleterious rare CELSR1 variants could be a possible cause of fetal hydrops.

LMNA Mutation in a Family with a Strong History of Sudden Cardiac Death

We report a family with heterozygous deletion of exons 3–6 of the LMNA gene. The main presentation of affected family members was characterized by ventricular and supraventricular arrhythmias, atrioventricular (AV) block and sudden cardiac death (SCD) but also by severe dilative cardiomyopathy (DCM). We report on two siblings, a 36-year-old female and her 40-year-old brother, who suffer from heart failure with mildly reduced ejection fraction, AV conduction delays and premature ventricular complexes. Their 65-year-old mother underwent heart transplantation at the age of 55 due to advanced heart failure. Originally, the LMNA mutation was detected in one of the uncles. This index patient and three of his brothers died of SCD as well as their father and aunt. The two siblings were treated with implanted defibrillators in our specialized tertiary heart failure center. This case report places this specific genetic variant in the context of LMNA-associated familial DCM.

Generalized Arterial Calcification of Infancy Type 1 (GACI1): Identification of a Novel Pathogenic Variant (c.1715T>C (p.Leu572Ser))

Generalized Arterial Calcification of Infancy (GACI) is a rare disease inherited in a recessive manner, with severe and diffuse early onset of calcifications along the internal elastic lamina in large and medium size arteries. The diagnosis results are from clinical manifestations, imaging, histopathologic exams, and genetic tests. GACI is predominantly caused by biallelic pathogenic variant in the ENPP1 gene (GACI1, OMIM#208000) and, to a lesser extent, by pathogenic variants in the ABCC6 gene (GACI2, OMIM#614473). We present a novel variation in the ENPP1 gene identified in a patient clinically diagnosed with GACI and confirmed by genetic investigation and autopsy as GACI type 1. The sequence analysis of the patient's ENPP1 gene detected two heterozygous variants c.1412A>G (p.Tyr471Cys) and c.1715T>C (p.Leu572Ser). The variant c.1715T>C (p.Leu572Ser) has not been described yet in the literature and in mutation databases. A genetic analysis was also carried out for the parents of the newborn; the heterozygous pathogenic variant c.1412A>G (p.Tyr471Cys) was detected in the mother's ENPP1 gene, and a sequence analysis of the father's ENPP1 gene revealed the novel heterozygous variant c.1715T>C (p.Leu572Ser). Our results showed that the variant c.1715T>C (p.Leu572Ser) may have a pathogenic role in the development of GACI type1 (GACI1, OMIM#208000), at least when associated with the pathogenic c.1412A>G (p.Tyr471Cys) variant. The identification of novel mutations potentially enabled genotype/phenotype associations that will ultimately have an impact on clinical management and prognosis for the disease.

The transcription factor Bcl11b promotes both canonical and adaptive NK cell differentiation

Epigenetic landscapes can provide insight into regulation of gene expression and cellular diversity. Here, we examined the transcriptional and epigenetic profiles of seven human blood natural killer (NK) cell populations, including adaptive NK cells. The BCL11B gene, encoding a transcription factor (TF) essential for T cell development and function, was the most extensively regulated, with expression increasing throughout NK cell differentiation. Several Bcl11b-regulated genes associated with T cell signaling were specifically expressed in adaptive NK cell subsets. Regulatory networks revealed reciprocal regulation at distinct stages of NK cell differentiation, with Bcl11b repressing RUNX2 and ZBTB16 in canonical and adaptive NK cells, respectively. A critical role for Bcl11b in driving NK cell differentiation was corroborated in BCL11B-mutated patients and by ectopic Bcl11b expression. Moreover, Bcl11b was required for adaptive NK cell responses in a murine cytomegalovirus model, supporting expansion of these cells. Together, we define the TF regulatory circuitry of human NK cells and uncover a critical role for Bcl11b in promoting NK cell differentiation and function.

Missense mutations in CASK, coding for the calcium-/calmodulin-dependent serine protein kinase, interfere with neurexin binding and neurexin-induced oligomerization

Mutations in the X-linked gene coding for the calcium-/calmodulin-dependent serine protein kinase (CASK) are associated with severe neurological disorders ranging from intellectual disability (in males) to mental retardation and microcephaly with pontine and cerebellar hypoplasia. CASK is involved in transcription control, in the regulation of trafficking of the post-synaptic NMDA and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors, and acts as a presynaptic scaffolding protein. For CASK missense mutations, it is mostly unclear which of CASK's molecular interactions and cellular functions are altered and contribute to patient phenotypes. We identified five CASK missense mutations in male patients affected by neurodevelopmental disorders. These and five previously reported mutations were systematically analysed with respect to interaction with CASK interaction partners by co-expression and co-immunoprecipitation. We show that one mutation in the L27 domain interferes with binding to synapse-associated protein of 97 kDa. Two mutations in the guanylate kinase (GK) domain affect binding of CASK to the nuclear factors CASK-interacting nucleosome assembly protein (CINAP) and T-box, brain, 1 (Tbr1). A total of five mutations in GK as well as PSD-95/discs large/ZO-1 (PDZ) domains affect binding of CASK to the pre-synaptic cell adhesion molecule Neurexin. Upon expression in neurons, we observe that binding to Neurexin is not required for pre-synaptic localization of CASK. We show by bimolecular fluorescence complementation assay that Neurexin induces oligomerization of CASK, and that mutations in GK and PDZ domains interfere with the Neurexin-induced oligomerization of CASK. Our data are supported by molecular modelling, where we observe that the cooperative activity of PDZ, SH3 and GK domains is required for Neurexin binding and oligomerization of CASK.

BCL11B mutations in patients affected by a neurodevelopmental disorder with reduced type 2 innate lymphoid cells

The transcription factor BCL11B is essential for development of the nervous and the immune system, and Bcl11b deficiency results in structural brain defects, reduced learning capacity, and impaired immune cell development in mice. However, the precise role of BCL11B in humans is largely unexplored, except for a single patient with a BCL11B missense mutation, affected by multisystem anomalies and profound immune deficiency. Using massively parallel sequencing we identified 13 patients bearing heterozygous germline alterations in BCL11B. Notably, all of them are affected by global developmental delay with speech impairment and intellectual disability; however, none displayed overt clinical signs of immune deficiency. Six frameshift mutations, two nonsense mutations, one missense mutation, and two chromosomal rearrangements resulting in diminished BCL11B expression, arose de novo. A further frameshift mutation was transmitted from a similarly affected mother. Interestingly, the most severely affected patient harbours a missense mutation within a zinc-finger domain of BCL11B, probably affecting the DNA-binding structural interface, similar to the recently published patient. Furthermore, the most C-terminally located premature termination codon mutation fails to rescue the progenitor cell proliferation defect in hippocampal slice cultures from Bcl11b-deficient mice. Concerning the role of BCL11B in the immune system, extensive immune phenotyping of our patients revealed alterations in the T cell compartment and lack of peripheral type 2 innate lymphoid cells (ILC2s), consistent with the findings described in Bcl11b-deficient mice. Unsupervised analysis of 102 T lymphocyte subpopulations showed that the patients clearly cluster apart from healthy children, further supporting the common aetiology of the disorder. Taken together, we show here that mutations leading either to BCL11B haploinsufficiency or to a truncated BCL11B protein clinically cause a non-syndromic neurodevelopmental delay. In addition, we suggest that missense mutations affecting specific sites within zinc-finger domains might result in distinct and more severe clinical outcomes.

Germline deletion of CIN85 in humans with X chromosome-linked antibody deficiency

Despite the numerous cellular functions attributed to the scaffolding protein CIN85, Keller et al. show that an inactivating germline deletion within the human CIN85 gene causes a remarkably specific defect in the activation of B lymphocytes, preventing proper immune responses.

Ubiquitously expressed Cbl-interacting protein of 85 kD (CIN85) is a multifunctional adapter molecule supposed to regulate numerous cellular processes that are critical for housekeeping as well as cell type–specific functions. However, limited information exists about the in vivo roles of CIN85, because only conditional mouse mutants with cell type–specific ablation of distinct CIN85 isoforms in brain and B lymphocytes have been generated so far. No information is available about the roles of CIN85 in humans. Here, we report on primary antibody deficiency in patients harboring a germline deletion within the CIN85 gene on the X chromosome. In the absence of CIN85, all immune cell compartments developed normally, but B lymphocytes showed intrinsic defects in distinct effector pathways of the B cell antigen receptor, most notably NF-κB activation and up-regulation of CD86 expression on the cell surface. These results reveal nonredundant functions of CIN85 for humoral immune responses.

A novel pathogenic MYH3 mutation in a child with Sheldon-Hall syndrome and vertebral fusions

Sheldon-Hall syndrome (SHS) is the most common of the distal arthrogryposes (DAs), a group of disorders characterized by congenital non-progressive contractures. Patients with SHS present with contractures of the limbs and a distinctive triangular facies with prominent nasolabial folds. Calcaneovalgus deformity is frequent, as well as camptodactyly and ulnar deviation. Causative mutations in at least four different genes have been reported (MYH3, TNNI2, TPM2, and TNNT3). MYH3 plays a pivotal role in fetal muscle development and mutations in this gene are associated with Freeman-Sheldon syndrome, distal arthrogryposis 8 (DA8), and autosomal dominant spondylocarpotarsal synostosis. The last two disorders are characterized by skeletal abnormalities, in particular bony fusions. The observation that MYH3 may be mutated in these syndromes has suggested the involvement of this gene in bone development. We report the case of a boy with a novel pathogenic MYH3 mutation, presenting with the classical clinical features of SHS in association with unilateral carpal bone fusion and multiple vertebral fusions. This distinctive phenotype has never been reported in the literature so far and expands the phenotypic spectrum of SHS, endorsing the clinical variability of patients with MYH3-related disorders. Our findings also support a role for MYH3 in both muscle and bone development, suggesting a phenotypic continuum in MYH3-related disorders.

Polymorphism of the brain-derived neurotrophic factor and dynamics of the seizure threshold of electroconvulsive therapy

During a course of electroconvulsive therapy (ECT), the level of currency necessary to induce an epileptic seizure in a patient may either remain relatively stable or-more often-may require repeated upward adjustment over time due to a constantly increasing seizure threshold. We aimed to determine whether a common polymorphism of the brain-derived neurotrophic factor (BDNF), which constitutes an important and ubiquitously expressed neurotrophine in the brain, affects the stimulation threshold of ECTs required to induce an epileptic seizure over time. Twenty-seven adult patients who underwent at least 12 consecutive ECT sessions were analyzed for the stimulation intensities required during the course of the stimulation as well as their BDNF gene status. We could not find a relation between the Val/Met polymorphism of the BDNF and the development of the seizure threshold during the course of the ECT sessions. Mechanisms and predispositions other than the BDNF polymorphism investigated in this study are responsible for the change in seizure thresholds over the course of ECT.

Microduplication of 3p26.3 in nonsyndromic intellectual disability indicates an important role of CHL1 for normal cognitive function

Terminal deletions of chromosome 3p26.3 confined to the CHL1 gene have previously been described in children with intellectual disability and epilepsy. Here, we report for the first time, a 3p26.3 duplication including only the CHL1 gene in an intellectually disabled girl with epilepsy. The penetrance of both deletions and duplications in 3p26.3 is reduced because all chromosomal imbalances were inherited from healthy parents. Further studies are needed to specify the pathogenic mechanism of 3p26.3 imbalances and to estimate recurrence risks in genetic counseling. However, the description of both deletions and duplications of chromosome 3p26.3 in nonsyndromic intellectual disability suggests that CHL1 is a dosage-sensitive gene with an important role for normal cognitive development.

A 3p interstitial deletion in two monozygotic twin brothers and an 18-year-old man: further characterization and review

An increasing number of patients with 3p proximal deletions were reported in the previous decade, but the region responsible for the main features such as intellectual disability (ID) and developmental delay is not yet characterized. Here we report on two monozygotic twin brothers of 2 10/12 years and an 18-year-old man, all three of them displaying severe ID, psychomotoric delay, autistic features, and only mild facial dysmorphisms. Array CGH (aCGH), revealed a 6.55 Mb de novo interstitial deletion of 3p14.1p14.3 in the twin brothers and a 4.76 Mb interstitial deletion of 3p14.1p14.2 in the 18-year-old patient, respectively. We compared the malformation spectrum with previous molecularly well-defined patients in the literature and in the DECIPHER database (Database of Chromosomal Imbalance and Phenotype in Humans using Ensembl Resources; http://decipher.sanger.ac.uk/). In conclusion, the deletion of a region containing 3p14.2 seems to be associated with a relative concise phenotype including ID and developmental delay. Thus, we hypothesize that 3p14.2 is the potential core region in 3p proximal deletions. The knowledge of this potential core region could be helpful in the genetic counselling of patients with 3p proximal deletions, especially concerning their phenotype.

Normal intelligence and premature ovarian failure in an adult female with a 7.6 Mb de novo terminal deletion of chromosome 9p

Distal deletion 9p is associated with gonadal dysfunction in XY individuals. Little is known about the gonadal function and fertility of XX females with this condition. We report on an affected 31-year-old infertile woman presenting with premature ovarian failure, mild dysmorphic features, a history of mild developmental delay and an otherwise normal female phenotype. Cytogenetic analysis showed a deletion 9p with the karyotype 46,XX,del(9)(p23-24) in lymphocytes. The subsequent oligonucleotide array-based CGH analysis with genomic DNA from peripheral blood revealed a terminal deletion of approximately 7.6 Mb. SNP microarray analyses of the patient and her unaffected parents confirmed the deletion breakpoint and revealed a de novo mutation of paternal origin. This is apparently the first description of an adult woman with a cytogenetically visible terminal deletion of chromosome 9p. The fertility problems observed in this patient complement earlier findings in prepubertal and pubertal 46,XX-girls with 9p deletions, who displayed a phenotype ranging from primary ovarian dysfunction and mild gonadotropin hyperresponses to positive menses. DMRT1 is hemizygous in our patient. We discuss the role of DMRT1 in female gonadal development.

Hereditary papillary renal cell carcinoma primarily diagnosed in a cervical lymph node: a case report of a 30-year-old woman with multiple metastases

Background

Papillary renal cell carcinoma is a rare cancer. Some cases can be attributed to individuals with hereditary renal cell carcinomas usually consisting of the clear cell subtype. In addition, two syndromes with hereditary papillary renal cell carcinoma have been described. One is the hereditary leiomyomatosis and renal cell carcinoma, which is characterized by cutaneous and uterine leiomyomas and renal cell carcinoma mostly consisting of the papillary renal cell carcinoma type II with a worse prognosis.

Case presentation

We describe a case of a 30-year-old woman with hereditary leiomyomatosis and renal cell carcinoma syndrome with extensively metastasized papillary renal cell carcinoma, primarily diagnosed in a cervical lymph node lacking leiomyomas at any site.

Conclusion

Papillary renal cell carcinoma in young patients should be further investigated for a hereditary variant like the hereditary leiomyomatosis and renal cell carcinoma even if leiomyomas could not be detected. A detailed histological examination and search for mutations is essential for the survival of patients and relatives.

Validation of three BRCA1/2 mutation-carrier probability models Myriad, BRCAPRO and BOADICEA in a population-based series of 183 German families

Many studies have evaluated the performance of risk assessment models for BRCA1/2 mutation carrier probabilities in different populations, but to our knowledge very few studies have been conducted in the German population so far. In the recent study, we validated the performance of three risk calculation models by names BRCAPRO, Myriad and BOADICEA in 183 German families who had undergone molecular testing of mutations in BRCA1 and BRCA2 with an indication based on clinical criteria regarding their family history of cancer. The sensitivity and specificity at the conventional threshold of 10% as well as for a threshold of 20% were evaluated. The ability to discriminate between carriers and non-carriers was judged by the area under the receiver operating characteristics curve. We further focused on the performance characteristic of these models in patients carrying large genomic rearrangements as a subtype of mutations which is currently gaining increasing importance. BRCAPRO and BOADICEA performed almost equally well in our patient population, but we found a lack of agreement to Myriad. The results obtained from this study were consistent with previously published results from other population and racial/ethnic groups. We suggest using model specific decision thresholds instead of the recommended universal value of 10%. We further suggest integrating the CaGene5 software package, which includes BRCAPRO and Myriad, in the genetic counselling of German families with suspected inherited breast and ovarian cancer because of the good performance of BRCAPRO and the substantial ease of use of this software.

A family with an inverted tandem duplication 5q22.1q23.2

Here, we report a 3-year-old boy with short stature, developmental delay and mild facial dysmorphic signs. Karyotype analysis and array-CGH revealed a pure duplication 5q22.1q23.2 with a length of 14.25 Mb. As demonstrated by multicolor-fluorescence in situ hybridization, the duplicated segment was orientated in an inverted tandem manner. One of the 2 older half-brothers of the index patient was intellectually disabled and showed short stature as well. The mother of the siblings was only 149 cm in height. The affected half-brother as well as the mother of the siblings were tested positive for the same duplication. Duplications of the long arm of chromosome 5 are rare. There are 16 reported cases of different 5q segments with a pure duplication and no additional chromosomal imbalance. In order to refine the 5q-duplication phenotype, reported cases were recently classified in 3 groups on the basis of clinical findings and the involved chromosome segments. However, our case does not fit in any of these groups but is placed in the interjacent chromosomal area between 2 of these groups. Overall, this is the second reported family with a duplication of 5q22.1q23.2 and both families share phenotypic features like short stature, facial dysmorphic signs and speech delay. The reported family provides further information for delineating phenotype-genotype correlations of pure duplications of the 5q region.

Mutation in the CPC motif-containing 6th transmembrane domain affects intracellular localization, trafficking and copper transport efficiency of ATP7A protein in mosaic mutant mice--an animal model of Menkes disease

Copper is an essential micronutrient for all living organisms. ATP7A protein is a copper-transporting ATPase which plays a vital role in the maintenance of cellular copper homeostasis in mammals. This protein is retained within the trans-Golgi network, but after binding copper it can be translocated to the cell membrane to participate in the efflux of excess Cu. Mutation of the ATP7A gene in humans results in the severe neurodegenerative disorder, Menkes disease. The mouse ATP7A homolog encodes a protein that plays the same role in copper transport. Mosaic mutant mice display a lethal phenotype which resembles Menkes disease, although the underlying molecular defect has not been characterized until now. In the present study we identified a G to C nucleotide exchange in exon 15 of the Atp7a gene in mosaic mutants, which resulted in an arginine to proline substitution in the highly conserved 6th transmembrane domain of the ATP7A protein. This mutated protein was mislocalized in kidney cells isolated from mosaic mutant mice, and following exposure of these cells to increased copper concentrations it was not translocated to the plasma membrane. Disturbance of ATP7A function in mosaic mice results in increased copper accumulation in the small intestine and kidneys, and in Cu deficiency in the brain, liver and heart. Mouse models of Menkes disease belong to the mottled mutant group. The mosaic mutant represents another interesting animal model for Menkes disease that will be of value in research on copper metabolism and transport in mammals.

Evaluating the effect of spastin splice mutations by quantitative allele-specific expression assay

BACKGROUND

mutations in the SPG4/SPAST gene are the most common cause for hereditary spastic paraplegia (HSP). The splice-site mutations make a significant contribution to HSP and account for 17.4% of all types of mutations and 30.8% of point mutations in the SPAST gene. However, only few studies with limited molecular approach were conducted to investigate and decipher the role of SPAST splice-site mutations in HSP.

METHODS

a reverse transcriptase-polymerase chain reaction (RT-PCR) analysis and quantitative allele-specific expression assay were performed.

RESULTS

we have characterized the consequence of two novel splice-site mutations (c.1493 + 1G>A and c.1414-1G>A) in the SPAST gene in two different families with pure HSP. The RT-PCR analysis revealed that both spastin mutations are indeed splice-site mutations and cause skipping of exon 12. Furthermore, RT-PCR data suggested that these splice-site mutations may cause leaky splicing. By means of a quantitative allele-specific expression assay, we could confirm that both splice-site mutations cause leaky splicing, as the relative expression of the exon 12-skipped transcript was reduced (21.1 ± 3.6 compared to expected 50%).

CONCLUSIONS

our finding supports a "threshold-effect-model" for functional spastin in HSP. A higher level (78.8 ± 3.9%) of functional spastin than the expected ratio of 50% owing to leaky splicing might cause late age at onset of HSP. Remarkably, we could show that a quantitative allele-specific expression assay is a simple and effective tool to evaluate the role of most types of spastin splice-site mutations in HSP.

Ring chromosome 22 and neurofibromatosis type II: proof of two-hit model for the loss of the NF2 gene in the development of meningioma

Carriers of a ring chromosome 22 are mentally retarded and show variable facial dysmorphism. They may also present with features of neurofibromatosis type II (NF2) such as vestibular schwannomas and multiple meningiomas. In these cases, tumourigenesis has been suspected to be caused by the loss of both alleles of the NF2 gene, a tumour suppressor localized in 22q12.2. Here, we describe an 18-year-old patient with constitutional ring chromosome 22 and mental retardation who developed rapid-onset spastic paraparesis at the age of 15 years. The causative spinal meningioma at the level of T3, which compressed the spinal cord, was surgically removed, and the patient regained ambulation. Array comparative genomic hybridization (array CGH) and multiplex ligation-dependent probe amplification (MLPA) analyses in blood revealed a terminal deletion in 22q13.32, not comprising the NF2 gene. In tumour tissue, loss of the whole ring chromosome 22 including one NF2 gene due to mitotic instability constituted the likely first hit, while a point mutation in the other allele of the NF2 gene (c.784C>T, p.R262X) was shown as second hit. We review all cases from the literature and suggest clinical guidelines for surveillance of patients with ring chromosome 22.

Functional evaluation of paraplegin mutations by a yeast complementation assay

An autosomal recessive form of hereditary spastic paraplegia (AR-HSP) is primarily caused by mutations in the SPG7 gene, which codes for paraplegin, a subunit of the hetero-oligomeric m-AAA protease in mitochondria. In the current study, sequencing of the SPG7 gene in the genomic DNA of 25 unrelated HSP individuals/families led to the identification of two HSP patients with compound heterozygous mutations (p.G349S/p.W583C and p.A510V/p.N739KfsX741) in the coding sequence of the SPG7 gene. We used a yeast complementation assay to evaluate the functional consequence of novel SPG7 sequence variants detected in the HSP patients. We assessed the proteolytic activity of hetero-oligomeric m-AAA proteases composed of paraplegin variant(s) and proteolytically inactive forms of AFG3L2 (AFG3L2(E575Q) or AFG3L2(K354A)) upon expression in m-AAA protease-deficient yeast cells. We demonstrate that the newly identified paraplegin variants perturb the proteolytic function of hetero-oligomeric m-AAA protease. Moreover, commonly occurring silent polymorphisms such as p.T503A and p.R688Q could be distinguished from mutations (p.G349S, p.W583C, p.A510V, and p.N739KfsX741) in our HSP cohort. The yeast complementation assay thus can serve as a reliable system to distinguish a pathogenic mutation from a silent polymorphism for any novel SPG7 sequence variant, which will facilitate the interpretation of genetic data for SPG7.

Pathways of proliferation and antiapoptosis driven in breast cancer stem cells by stem cell protein piwil2

Cancer stem cell studies may improve understanding of tumor pathophysiology and identify more effective strategies for cancer treatment. In a variety of organisms, Piwil2 has been implicated in multiple roles including stem cell self-renewal, RNA silencing, and translational control. In this study, we documented specific expression of the stem cell protein Piwil2 in breast cancer with predominant expression in breast cancer stem cells. In patients who were evaluated, we determined that 90% of invasive carcinomas and 81% of carcinomas in situ exhibited highest expression of Piwil2. In breast cancer cells, Piwil2 silencing suppressed the expression of signal transducer and activator of transcription 3, a pivotal regulator of Bcl-X(L) and cyclin D1, whose downregulation paralleled a reduction in cell proliferation and survival. Our findings define Piwil2 and its effector signaling pathways as key factors in the proliferation and survival of breast cancer stem cells.

Brain-derived neurotrophic factor (BDNF) gene polymorphisms shape cortical plasticity in humans

BACKGROUND

The brain-derived neurotrophic factor (BDNF) gene is involved in mechanisms of synaptic plasticity in the adult brain. It has been demonstrated that BDNF also plays a significant role in shaping externally induced human brain plasticity. Plasticity induced in the human motor cortex by intermittent theta-burst stimulation (iTBS) was impaired in individuals expressing the Val66Met polymorphism.

METHODS

To explore whether this polymorphism is also important for other neuroplasticity-inducing tools in humans with modes of action differing from that of iTBS, namely, transcranial direct current (tDCS) and random noise stimulation (tRNS), we retrospectively analyzed the data of 64 subjects studied in our laboratory with regard to BDNF genotype.

RESULTS

Fifteen subjects with the Val66Met allele, 46 subjects with the Val66Val allele, and 3 Met66Met carriers were identified. The response of the Val66Met allele carriers to stimulation differed in two protocols compared with the response of Val66Val individuals. For iTBS (15 subjects, 5 heterozygotes), plasticity could be only induced in the Val66Val allele carriers. However, for facilitatory tDCS (24 subjects, 10 heterozygotes), as well as for inhibitory tDCS, (19 subjects, 8 heterozygotes), carriers of the Val66Met allele displayed enhanced plasticity, whereas for transcranial random noise stimulation (29 subjects, 8 heterozygotes), the difference between groups was not so pronounced.

CONCLUSIONS

BDNF polymorphism has a definite impact on plasticity in humans, which might differ according to the mechanism of plasticity induction. This impact of BDNF on plasticity should be taken into account for future studies, as well as having wider ranging implications for the treatment of neuropsychiatric disorders with transcranial stimulation tools, as it may predetermine their efficacy for the treatment of disease and rehabilitation.

A newborn with hereditary haemorrhagic telangiectasia and an unusually severe phenotype

Hereditary haemorrhagic telangiectasia (HHT), associated with arteriovenous malformations, is a genetic disease of the vascular system with a frequency of approx. 1:10,000. Genetic diagnosis serves to identify individuals at risk of developing the disease and is a useful tool for genetic counselling purposes.

QUESTIONS UNDER STUDY

Here we report on a child presenting severe arteriovenous malformations leading to heart failure. Her mother and grandmother present fewer symptoms of hereditary haemorrhagic telangiectasia. In this study we identify the cause of HHT in the family.

METHODS

Clinical examination, PCR, DNA sequencing, quantitative PCR, Southern blot, xray, ultrasound, cardiac catheterisation and angiocardiography.

RESULTS

Initially the sequence variant in c.392C>T in the endoglin gene was detected in the grandmother, but not in other affected family members. Further analyses revealed a deletion of exon 1 of endoglin, segregating with the phenotype.

CONCLUSIONS

This report points out the need for careful evaluation of molecular genetic findings, particularly in diseases with highly variable phenotype.

Expansion of mutation spectrum, determination of mutation cluster regions and predictive structural classification of SPAST mutations in hereditary spastic paraplegia

The SPAST gene encoding for spastin plays a central role in the genetically heterogeneous group of diseases termed hereditary spastic paraplegia (HSP). In this study, we attempted to expand and refine the genetic and phenotypic characteristics of SPAST associated HSP by examining a large cohort of HSP patients/families. Screening of 200 unrelated HSP cases for mutations in the SPAST gene led to detection of 57 mutations (28.5%), of which 47 were distinct and 29 were novel mutations. The distribution analysis of known SPAST mutations over the structural domains of spastin led to the identification of several regions where the mutations were clustered. Mainly, the clustering was observed in the AAA (ATPases associated with diverse cellular activities) domain; however, significant clustering was also observed in the MIT (microtubule interacting and trafficking), MTBD (microtubule-binding domain) and an N-terminal region (228-269 residues). Furthermore, we used a previously generated structural model of spastin as a framework to classify the missense mutations in the AAA domain from the HSP patients into different structural/functional groups. Our data also suggest a tentative genotype-phenotype correlation and indicate that the missense mutations could cause an earlier onset of the disease.

A newborn with hereditary haemorrhagic telangiectasia and an unusually severe phenotype

Hereditary haemorrhagic telangiectasia (HHT), associated with arteriovenous malformations, is a genetic disease of the vascular system with a frequency of approx. 1:10,000. Genetic diagnosis serves to identify individuals at risk of developing the disease and is a useful tool for genetic counselling purposes.

QUESTIONS UNDER STUDY

Here we report on a child presenting severe arteriovenous malformations leading to heart failure. Her mother and grandmother present fewer symptoms of hereditary haemorrhagic telangiectasia. In this study we identify the cause of HHT in the family.

METHODS

Clinical examination, PCR, DNA sequencing, quantitative PCR, Southern blot, xray, ultrasound, cardiac catheterisation and angiocardiography.

RESULTS

Initially the sequence variant in c.392C>T in the endoglin gene was detected in the grandmother, but not in other affected family members. Further analyses revealed a deletion of exon 1 of endoglin, segregating with the phenotype.

CONCLUSIONS

This report points out the need for careful evaluation of molecular genetic findings, particularly in diseases with highly variable phenotype.