Disruption of the methyltransferase-like 23 gene METTL23 causes mild autosomal recessive intellectual disability.

We describe the characterization of a gene for mild nonsyndromic autosomal recessive intellectual disability (ID) in two unrelated families, one from Austria, the other from Pakistan. Genome-wide single nucleotide polymorphism microarray analysis enabled us to define a region of homozygosity by descent on chromosome 17q25. Whole-exome sequencing and analysis of this region in an affected individual from the Austrian family identified a 5 bp frameshifting deletion in the METTL23 gene. By means of Sanger sequencing of METTL23, a nonsense mutation was detected in a consanguineous ID family from Pakistan for which homozygosity-by-descent mapping had identified a region on 17q25. Both changes lead to truncation of the putative METTL23 protein, which disrupts the predicted catalytic domain and alters the cellular localization. 3D-modelling of the protein indicates that METTL23 is strongly predicted to function as an S-adenosyl-methionine (SAM)-dependent methyltransferase. Expression analysis of METTL23 indicated a strong association with heat shock proteins, which suggests that these may act as a putative substrate for methylation by METTL23. A number of methyltransferases have been described recently in association with ID. Disruption of METTL23 presented here supports the importance of methylation processes for intact neuronal function and brain development.

AKR1B10 expression is associated with less aggressive hepatocellular carcinoma: a clinicopathological study of 168 cases.

BACKGROUND/AIMS: The detoxification enzyme AKR1B10, a member of the aldo-keto reductase superfamily, is discussed as a new biomarker candidate for hepatocellular carcinoma (HCC). Only rare clinicopathological data on AKRB1B10 in HCC exist. This retrospective study determines the diagnostic and prognostic relevance of AKR1B10 expression in HCC and its relationship to a series of clinicopathological parameters including underlying aetiological factors. METHODS: A series of 168 patients with HCCs treated either by surgical resection (n=92) or liver transplantation (n=76) were investigated after construction of a tissue micro-array. Immunohistochemically confirmed AKR1B10 expression was correlated with clinicopathologically relevant parameters as well as proliferative activity (indicated by Ki-67 immunostaining) and apoptosis (terminal deoxyribonucleotide transferase-mediated dUTP nick-end labelling). RESULTS: AKR1B10 overexpression is significantly associated with lower pT-classification (P=0.030) and highly statistically associated with an underlying viral hepatitis (P<0.001) and the presence of cirrhosis (P<0.001). In addition, loss of AKR1B10 expression correlates with increased proliferative activity (Ki-67, P=0.001). Kaplan-Meier survival analysis of the resection group reveals a poorer prognosis in patients with AKR1B10-negative HCCs compared with patients with strongly positive HCCs (P=0.046). CONCLUSIONS: This study confirms and expands data on the expression of AKR1B10 in HCC, suggesting that this enzyme is a valuable novel biomarker candidate for staging of HCC, especially in patients with underlying virus hepatitis or cirrhosis, and may present a new therapeutic target for multimodal therapy concepts. We confirm its prognostic value and conclude that high expression of AKR1B10 reflects a less aggressive tumour behaviour.

Phenotypic variability of a deletion and duplication 6q16.1 → q21 due to a paternal balanced ins(7;6)(p15;q16.1q21).

Constitutional insertional translocations are rare findings in clinical cytogenetics. Here, we report on the unbalanced segregation of a balanced paternal insertional translocation ins(7;6)(p15;q16.1q21) to three children. Investigations by conventional karyotyping, FISH with locus-specific probes, microsatellite marker analysis, and SNP-array based copy number analysis revealed a direct orientation of the inserted segment, a size of 11.3 Mb, and breakpoints between rs4370337 and rs12660854 and rs12110990 and rs4946730 on 6q16.1 and 6q21, respectively, as well as within BAC clone RP11-182J2 on 7p15. A 17-year-old daughter inherited the der(6) chromosome and was affected by severe mental retardation, obesity, and minor anomalies. Two further children inherited the der(7) chromosome. A daughter shows an almost unremarkable phenotype and only minor features in neuropsychological testing at 19 years of age. Her 14-year-old half-brother demonstrates a mild delay in cognitive development most likely jointly caused by the chromosomal rearrangement and asphyxia during delivery. The patient with the deletion confirms the previously reported phenotype of severe mental retardation and obesity in patients with del(6)(q16.2), while both patients with partial trisomy for the same segment of chromosome 6 are further examples for a generally less severe phenotype associated with duplications than with deletions, and even for the recent insight that chromosomal aneusomies of several megabases may go without major clinical consequences.

"Essentially" pure trisomy 3q27 --> qter: further delineation of the partial trisomy 3q phenotype.

Partial duplication 3q is a well defined clinical entity characterized by growth retardation, cryptorchism, microcephaly, and characteristic dysmorphisms. Most patients present with large duplications or are associated with a second chromosomal imbalance, which makes the definition of the phenotype difficult. Here, we report on a 4-year and 8-month-old girl with pre- and postnatal measurements in the high normal range, developmental delay, minor dysmorphic features, and a de novo unbalanced 3/4 translocation with trisomy 3q27 --> qter and monosomy of the subtelomeric region of 4p. Conventional karyotyping, FISH with probes from the Wolf-Hirschhorn syndrome critical region and chromosome 4p locus-specific probes, microsatellite marker-based haplotyping, and SNP microarray copy number analysis revealed a terminal 4p deletion of less than 500 kb with a breakpoint distal to the Wolf-Hirschhorn syndrome critical region, a chromosome 3q duplication of around 15.3 Mb, with origin of the rearrangement in paternal meiosis. Thus, our case clearly characterizes the phenotype of pure partial duplication 3q more exactly, and moreover, indicates that small chromosome rearrangements might lead to growth in the upper normal range or even cause overgrowth.

Conditional control of fluorescent protein degradation by an auxin-dependent nanobody.

The conditional and reversible depletion of proteins by auxin-mediated degradation is a powerful tool to investigate protein functions in cells and whole organisms. However, its wider applications require fusing the auxin-inducible degron (AID) to individual target proteins. Thus, establishing the auxin system for multiple proteins can be challenging. Another approach for directed protein degradation are anti-GFP nanobodies, which can be applied to GFP stock collections that are readily available in different experimental models. Here, we combine the advantages of auxin and nanobody-based degradation technologies creating an AID-nanobody to degrade GFP-tagged proteins at different cellular structures in a conditional and reversible manner in human cells. We demonstrate efficient and reversible inactivation of the anaphase promoting complex/cyclosome (APC/C) and thus provide new means to study the functions of this essential ubiquitin E3 ligase. Further, we establish auxin degradation in a vertebrate model organism by employing AID-nanobodies in zebrafish.

Quantitative Cell Cycle Analysis Based on an Endogenous All-in-One Reporter for Cell Tracking and Classification.

Cell cycle kinetics are crucial to cell fate decisions. Although live imaging has provided extensive insights into this relationship at the single-cell level, the limited number of fluorescent markers that can be used in a single experiment has hindered efforts to link the dynamics of individual proteins responsible for decision making directly to cell cycle progression. Here, we present fluorescently tagged endogenous proliferating cell nuclear antigen (PCNA) as an all-in-one cell cycle reporter that allows simultaneous analysis of cell cycle progression, including the transition into quiescence, and the dynamics of individual fate determinants. We also provide an image analysis pipeline for automated segmentation, tracking, and classification of all cell cycle phases. Combining the all-in-one reporter with labeled endogenous cyclin D1 and p21 as prime examples of cell-cycle-regulated fate determinants, we show how cell cycle and quantitative protein dynamics can be simultaneously extracted to gain insights into G1 phase regulation and responses to perturbations.