Monoallelic Loss-of-Function IFT140 Pathogenic Variants Cause Autosomal Dominant Polycystic Kidney Disease: A Confirmatory Study With Suspicion of an Additional Cardiac Phenotype.

Autosomal dominant polycystic kidney disease (ADPKD) is the most common inherited kidney disease. While biallelic variants affecting IFT140 are responsible for Mainzer-Saldino syndrome (characterized by severe ciliopathy causing skeletal abnormalities, kidney disease, and cysts), monoallelic loss-of-function (LoF) variants have been recently reported as an important cause of ADPKD beyond PKD1/2 genes. Herein, we report 6 non-family-related cases of monoallelic IFT140 LoF variants, identified from 1,340 exomes sequenced for nephrological indications in our local database. Every patient presented with polycystic kidney disease. Furthermore, the mother of a boy diagnosed with Mainzer-Saldino syndrome with a biallelic variant affecting IFT140 presented with several bilateral cysts, revealed after kidney imaging, and was found to carry a pathologic frameshift IFT140 variation. As well as this particular Mainzer-Saldino case, our 6 additional patients confirm that heterozygous IFT140 frameshift variants are responsible for the cystic phenotype and kidney failure. Interestingly, of the 6 patients, 2 also exhibited dilated cardiomyopathy, which was of unknown origin, as no genetic cause was found after exome sequencing analysis, suggesting a potential connection between IFT140 and heart disease.

Mutational Characteristics of Primary Mucosal Melanoma: A Systematic Review.

BACKGROUND: Primary mucosal melanomas (PMMs) are rare and clinically heterogeneous, including head and neck (HNMs), vulvovaginal (VVMs), conjunctival (CjMs), anorectal (ARMs) and penile (PMs) melanomas. While the prognosis of advanced cutaneous melanoma has noticeably improved using treatments with immune checkpoint inhibitors (ICIs) and molecules targeting BRAF and MEK, few advances have been made for PMMs because of their poorer response to ICIs and their different genetic profile. This prompted us to conduct a systematic review of molecular studies of PMMs to clarify their pathogenesis and potential therapeutic targets. METHODS: All articles that examined gene mutations in PMMs were identified from the databases and selected based on predefined inclusion criteria. Mutation rate was calculated for all PMMs and each location group by relating the number of mutations identified to the total number of samples analysed. RESULTS: Among 1,581 studies identified, 88 were selected. Overall, the frequency of KIT, BRAF and NRAS mutation was 13.5%, 12.9% and 12.1%, respectively. KIT mutation ranged from 6.4% for CjMs to 16.6% for ARMs, BRAF mutation from 8.6% for ARMs to 31.1% for CjMs, and NRAS mutation from 6.2% for ARMs to 18.5% for CjMs. Among 101 other genes analysed, 33 had mutation rates over 10%, including TTN, TSC1, POM121, NF1, MTOR and SF3B1. CONCLUSION: In addition to BRAF, NRAS and KIT genes commonly studied, our systematic review identified significantly mutated genes that have already been associated (e.g., TSC1, mTOR, POLE or ATRX) or could be associated with (future) targeted therapies. PROSPERO ID: CRD42020185552.

LRP1 expression in colon cancer predicts clinical outcome.

LRP1 (low-density lipoprotein receptor-related protein 1), a multifunctional endocytic receptor, has recently been identified as a hub within a biomarker network for multi-cancer clinical outcome prediction. As its role in colon cancer has not yet been characterized, we here investigate the relationship between LRP1 and outcome. MATERIALS AND METHODS: LRP1 mRNA expression was determined in colon adenocarcinoma and paired colon mucosa samples, as well as in stromal and tumor cells obtained after laser capture microdissection. Clinical potential was further investigated by immunohistochemistry in a population-based colon cancer series (n = 307). LRP1 methylation, mutation and miR-205 expression were evaluated and compared with LRP1 expression levels. RESULTS: LRP1 mRNA levels were significantly lower in colon adenocarcinoma cells compared with colon mucosa and stromal cells obtained after laser capture microdissection. Low LRP1 immunohistochemical expression in adenocarcinomas was associated with higher age, right-sided tumor, loss of CDX2 expression, Annexin A10 expression, CIMP-H, MSI-H and BRAFV600E mutation. Low LRP1 expression correlated with poor clinical outcome, especially in stage IV patients. While LRP1 expression was downregulated by LRP1 mutation, LRP1 promoter was never methylated. CONCLUSIONS: Loss of LRP1 expression is associated with worse colon cancer outcomes. Mechanistically, LRP1 mutation modulates LRP1 expression.

Resveratrol attenuates oxidative stress in mitochondrial Complex I deficiency: Involvement of SIRT3.

The pathophysiological mechanisms underlying Complex I (CI) deficiencies are understood only partially which severely limits the treatment of this common, devastating, mitochondrial disorder. Recently, we have shown that resveratrol (RSV), a natural polyphenol, has beneficial effects on CI deficiency of nuclear origin. Here, we demonstrate that RSV is able to correct the biochemical defect in oxygen consumption in five of thirteen CI-deficient patient cell lines. Other beneficial effects of RSV include a decrease of total intracellular ROS and the up-regulation of the expression of mitochondrial superoxide dismutase (SOD2) protein, a key antioxidant defense enzyme. The molecular mechanisms leading to the up-regulation of SOD2 protein expression by RSV require the estrogen receptor (ER) and the estrogen-related receptor alpha (ERRα). Although RSV increases the level of SOD2 protein in patients' fibroblasts, the enzyme activity is not increased, in contrast to normal fibroblasts. This led us to hypothesize that SOD2 enzyme activity is regulated post-translationally. This regulation involves SIRT3, a mitochondrial NAD(+)-dependent deacetylase and is critically dependent on NAD(+) levels. Taken together, our data show that the metabolic effects of RSV combined with its antioxidant capacities makes RSV particularly interesting as a candidate molecule for the therapy of CI deficiencies.

Assembly defects induce oxidative stress in inherited mitochondrial complex I deficiency.

Complex I (CI) deficiency is the most common respiratory chain defect representing more than 30% of mitochondrial diseases. CI is an L-shaped multi-subunit complex with a peripheral arm protruding into the mitochondrial matrix and a membrane arm. CI sequentially assembled into main assembly intermediates: the P (pumping), Q (Quinone) and N (NADH dehydrogenase) modules. In this study, we analyzed 11 fibroblast cell lines derived from patients with inherited CI deficiency resulting from mutations in the nuclear or mitochondrial DNA and impacting these different modules. In patient cells carrying a mutation located in the matrix arm of CI, blue native-polyacrylamide gel electrophoresis (BN-PAGE) revealed a significant reduction of fully assembled CI enzyme and an accumulation of intermediates of the N module. In these cell lines with an assembly defect, NADH dehydrogenase activity was partly functional, even though CI was not fully assembled. We further demonstrated that this functional N module was responsible for ROS production through the reduced flavin mononucleotide. Due to the assembly defect, the FMN site was not re-oxidized leading to a significant oxidative stress in cell lines with an assembly defect. These findings not only highlight the relationship between CI assembly and oxidative stress, but also show the suitability of BN-PAGE analysis in evaluating the consequences of CI dysfunction. Moreover, these data suggest that the use of antioxidants may be particularly relevant for patients displaying a CI assembly defect.

Stuve-Wiedemann syndrome: is it underrecognized?

Stuve-Wiedemann Syndrome (SWS) (OMIM #601559) is an autosomal recessive disorder characterized by skeletal changes, bowing of the lower limb, severe osteoporosis and joint contractures, episodic hyperthermia, frequent respiratory infections, feeding problems and high mortality in early life. It is caused by mutation in the leukemia inhibitory factor receptor gene (LIFR; 151443) on chromosome 5p13. We provide the clinical follow-up and molecular aspects of six new patients who carried the same novel mutation in the LIFR gene (p.Arg692X) and three patients carried a common haplotype at the LIFR locus supporting a founder effect in the Turkish population. The probable pathogenesis of the features is also discussed. Osseous findings in the presence of other above-mentioned morbid conditions should raise the suspicion of SWS in neonates especially in Arabic and Eastern Mediterranean countries with high rate of consanguineous marriages like in Turkey. Severe osteoporosis, bone deformities, milias, leukocoria, inflammatory lesions on distal extremities, tongue biting behavior and oral ulcers could be more prominent features of the survivors beyond the neonatal period while respiratory and feeding problems are remitting. It is of crucial importance to diagnose such babies earlier in order to prevent extensive laboratory workup and to provide proper genetic counseling.

Amyloid precursor-like protein 2 cleavage contributes to neuronal intranuclear inclusions and cytotoxicity in spinocerebellar ataxia-7 (SCA7).

In spinocerebellar ataxia-7 (SCA7), a polyglutamine (polyQ) expansion in the ataxin-7 protein leads to the formation of neuronal intranuclear inclusions (NIIs) and neurodegeneration. In this study, amyloid precursor-like protein 2 (APLP2) was identified as a partner protein for ataxin-7. APLP2, belonging to the APP gene family, undergoes secretase and caspase cleavages and has been implicated in the pathogenesis of Alzheimer's disease (AD). Activated caspase-3 cleaves APP family proteins to release N-terminal fragments (NTFs) and intracellular C-terminal domains (ICDs), which can translocate into the nucleus and induce neurotoxicity in AD. Here, we report abnormal nuclear relocation of APLP2 and detection of NTFs in NIIs in SCA7. The ICDs generated by caspase-3 cleavage of APLP2 accumulate in nuclei and contribute to a cumulative toxicity when coexpressed with mutated ataxin-7. Our data suggest that the interaction between APLP2 and ataxin-7 and proteolytic processing of APLP2 may contribute to the pathogenesis of SCA7.

Spectrum of HNF1B mutations in a large cohort of patients who harbor renal diseases.

BACKGROUND AND OBJECTIVES: Hepatocyte nuclear factor 1beta (HNF1beta) is a transcription factor that is critical for the development of kidney and pancreas. In humans, mutations in HNF1B lead to congenital anomalies of the kidney and urinary tract, pancreas atrophy, and maturity-onset diabetes of the young type 5 and genital malformations. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: We report HNF1B screening in a cohort of 377 unrelated cases with various kidney phenotypes (hyperechogenic kidneys with size not more than +3 SD, multicystic kidney disease, renal agenesis, renal hypoplasia, cystic dysplasia, or hyperuricemic tubulointerstitial nephropathy not associated with UMOD mutation). RESULTS: We found a heterozygous mutation in 75 (19.9%) index cases, consisting of a deletion of the whole gene in 42, deletion of one exon in one, and small mutations in 32. Eighteen mutations were novel. De novo mutations accounted for 66% of deletions and 40% of small mutations. In patients who carried HNF1B mutation and for whom we were able to study prenatal ultrasonography (56 probands), isolated hyperechogenic kidneys with normal or slightly enhanced size were the more frequent (34 of 56) phenotype before birth. Various other prenatal renal phenotypes were associated with HNF1B mutations, at a lesser frequency. Diabetes developed in four probands. Hyperuricemia and hypomagnesemia, although not systematically investigated, were frequently associated. CONCLUSIONS: This large series showed that the severity of the renal disease associated with HNF1B mutations was extremely variable (from prenatal renal failure to normal renal function in adulthood) and was not correlated with the genotype.

Pearson syndrome in the neonatal period: two case reports and review of the literature.

Pearson syndrome is a multiorgan mitochondrial cytopathy that results from defective oxidative phosphorylation owing to mitochondrial DNA deletions. Prognosis is severe and death occurs in infancy or early childhood. This article describes 2 cases with a severe neonatal onset of the disease. A review of the literature reveals the atypical presentation of the disease in the neonatal period, which is often overlooked and underdiagnosed.

Maternal uniparental heterodisomy of chromosome 17 in a patient with nephropathic cystinosis.

We report maternal uniparental disomy of chromosome 17 (mat UPD17) in a 2.5-year-old girl presenting infantile cystinosis. This patient was homozygous for the 57 kb deletion encompassing the CTNS gene, frequently found in patients from the European origin. The proband's mother was heterozygous for the deletion and the father did not carry the deletion. We carried out haplotype analysis with polymorphic markers spanning the whole chromosome 17. Informative markers showed the presence of two maternal alleles but no paternal allele for regions spanning the 17q arm and the proximal half of 17p, and only one maternal allele on the distal 17p arm. As deletion of half of 17p is probably not viable, these results suggest mat UPD17 with heterodisomy of 17q and proximal 17p and isodisomy of distal 17p. This is the first demonstration of mat UPD17, in particular of isodisomy 17p, in cystinosis.

Amyotrophic lateral sclerosis with neuronal intranuclear protein inclusions.

A 46-year-old patient developed amyotrophic lateral sclerosis (ALS) characterized by rapid progression. She needed respiratory assistance after a course of 9 months. She died 4.5 years after onset. Autopsy showed dramatic atrophy of the spinal cord, sparing only the posterior tracts, associated with neuronal loss and astrogliosis in various areas including the anterior horns, motor cortex, striatum, thalamus, and substantia nigra. Ubiquitin immunohistochemistry showed rare skein-like inclusions in the surviving spinal and medullary motor neurons. Eosinophilic inclusions were found in the nuclei of pyramidal neurons in the hippocampus. These inclusions were immunoreactive to antibodies against ubiquitin, promyelocytic leukemia gene product, proteasome, and ataxin-3. They were not immunoreactive to antibodies against tau, cystatin C, neurofilament, alpha-synuclein, SOD-1, and polyglutamine (1C2), and were not stained by ethidium bromide. Similar inclusions were found in the motor cortex. The immunoreactivity of the inclusions was similar to that encountered in diseases associated with CAG repeats, except for the negativity of the immunolabelling with 1C2. At the ultrastructural level, the nuclear inclusions were made of straight filaments (10-12 nm in diameter) arranged at random, reminiscent of the polyglutamine intranuclear hyaline inclusions.

PML nuclear bodies and neuronal intranuclear inclusion in polyglutamine diseases.

In polyglutamine diseases, accumulation in the nucleus of mutant proteins induces the formation of neuronal intranuclear inclusions (NIIs). The nucleus is compartmentalized into structural and functional domains, which are involved in NII formation. Promyelocytic leukemia protein (PML), a major component of nuclear bodies, and mSin3A, a component of the transcription co-repressor complex, were used to investigate how the intranuclear domains/sites relate to NII formation in SCA2, SCA3, SCA7, SCA17 and DRPLA brains. We demonstrate that the size of PML-positive intranuclear structures was larger in pathological brains than in control ones and that these structures contained mutant proteins. PML colocalized only with small NIIs, which maintained the ring-like structure of normal nuclear bodies. Enlarged ring-like PML-positive structures, devoid of mutant proteins, were also found and might represent structures where mutant polyglutamine proteins have been successfully processed. These data suggest that NIIs originate from nuclear bodies, where mutant proteins accumulate for degradation.

Two populations of neuronal intranuclear inclusions in SCA7 differ in size and promyelocytic leukaemia protein content.

Spinocerebellar ataxia type 7 (SCA7) is a hereditary progressive cerebellar ataxia with retinal degeneration associated with an abnormally expanded polyglutamine stretch. Neuronal intranuclear inclusions (NIIs), as in other polyglutamine diseases, are pathological hallmarks of these disorders. NIIs in polyglutamine diseases contain not only the protein with the expanded polyglutamine stretch but also other types of proteins. Several chaperone proteins related to the ubiquitin proteasome pathway, transcription factors and nuclear matrix proteins have been detected in NIIs. The composition of NIIs might reflect the process of NII formation and part of the pathogenesis of these diseases. To investigate how these proteins relate to the pathogenesis of SCA7, we performed immunohistochemical analyses of the composition of NIIs in two cases of SCA7. We demonstrated that there are two types of NIIs in SCA7 that differ in size and immunoreactivity to promyelocytic leukaemia protein (PML), one of the essential components of nuclear bodies (NBs; also called PML oncogenic domains). Small and large NIIs contained ataxin-7, human DnaJ homologue 2 (HDJ-2) and proteasome subunit 19S. In contrast, PML was found only in small NIIs. CREB-binding protein (CBP), another component of NBs, was distributed like PML in NIIs. Our results suggest that NIIs are formed by the accumulation of ataxin-7 in NBs, which become enlarged as they recruit related proteins.