Heterozygous ANKRD17 loss-of-function variants cause a syndrome with intellectual disability, speech delay, and dysmorphism.

ANKRD17 is an ankyrin repeat-containing protein thought to play a role in cell cycle progression, whose ortholog in Drosophila functions in the Hippo pathway as a co-factor of Yorkie. Here, we delineate a neurodevelopmental disorder caused by de novo heterozygous ANKRD17 variants. The mutational spectrum of this cohort of 34 individuals from 32 families is highly suggestive of haploinsufficiency as the underlying mechanism of disease, with 21 truncating or essential splice site variants, 9 missense variants, 1 in-frame insertion-deletion, and 1 microdeletion (1.16 Mb). Consequently, our data indicate that loss of ANKRD17 is likely the main cause of phenotypes previously associated with large multi-gene chromosomal aberrations of the 4q13.3 region. Protein modeling suggests that most of the missense variants disrupt the stability of the ankyrin repeats through alteration of core structural residues. The major phenotypic characteristic of our cohort is a variable degree of developmental delay/intellectual disability, particularly affecting speech, while additional features include growth failure, feeding difficulties, non-specific MRI abnormalities, epilepsy and/or abnormal EEG, predisposition to recurrent infections (mostly bacterial), ophthalmological abnormalities, gait/balance disturbance, and joint hypermobility. Moreover, many individuals shared similar dysmorphic facial features. Analysis of single-cell RNA-seq data from the developing human telencephalon indicated ANKRD17 expression at multiple stages of neurogenesis, adding further evidence to the assertion that damaging ANKRD17 variants cause a neurodevelopmental disorder.

Expert Opinions on Managing Fertility and Pregnancy in Patients With Mucopolysaccharidosis

Abstract The mucopolysaccharidosis (MPS) disorders are rare genetic diseases caused by deficiencies in lysosomal enzymes involved in the degradation of glycosaminoglycans, leading to pulmonary, cardiac and neurological dysfunctions, skeletal anomalies, impaired vision, and/or hearing and shortened life spans. Whereas in the past, few individuals with MPS reached adulthood, better diagnosis, multidisciplinary care, and new therapies have led to an increasing number of adult patients with MPS. Therefore, fertility and pregnancy questions in this patient population are becoming more important. Management of fertility issues and pregnancy in patients with MPS is challenging due to the lack of documented cases and a dearth in the literature on this topic. This review presents multidisciplinary expert opinions on managing fertility and pregnancy based on case studies and clinical experience presented at a meeting of MPS specialists held in Berlin, Germany, in April 2015. An overview of the existing literature on this subject is also included.

Measuring mRNA stability during early Drosophila embryogenesis.

Maternal mRNAs play a major role in directing early Drosophila melanogaster development, and thus, precise posttranscriptional regulation of these messages is imperative for normal embryogenesis. Although initially abundant on egg deposition, a subset of these maternal mRNAs is targeted for destruction during the first 2 to 3 h of embryogenesis. In this chapter, we describe molecular methods to determine the kinetics and mechanisms of maternal mRNA decay in the early D. melanogaster embryo. We show how both unfertilized eggs and fertilized embryos can be used to identify maternal mRNAs destined for degradation, to explain changes in decay kinetics over time, and to uncover the molecular mechanisms of targeted maternal mRNA turnover. In the first section, we explore the methods and outcomes of measuring decay on a "gene-by-gene" basis, which involves examination of a small number of transcripts by Northern blotting, RNA dot blotting, and real-time RT-PCR. In the second section, we provide a comprehensive examination of the applications of microarray technology to study global changes in maternal mRNA decay during early development. Genome-wide surveys of maternal mRNA turnover provide a wealth of information regarding the magnitude, temporal regulation, and genetic control of maternal mRNA turnover. Methods that permit the collection and analysis of highly reproducible and statistically robust data in this developmental system are discussed.

Drosophila maternal Hsp83 mRNA destabilization is directed by multiple SMAUG recognition elements in the open reading frame.

SMAUG (SMG) is an RNA-binding protein that functions as a key component of a transcript degradation pathway that eliminates maternal mRNAs in the bulk cytoplasm of activated Drosophila melanogaster eggs. We previously showed that SMG destabilizes maternal Hsp83 mRNA by recruiting the CCR4-NOT deadenylase to trigger decay; however, the cis-acting elements through which this was accomplished were unknown. Here we show that Hsp83 transcript degradation is regulated by a major element, the Hsp83 mRNA instability element (HIE), which maps to a 615-nucleotide region of the open reading frame (ORF). The HIE is sufficient for association of a transgenic mRNA with SMG protein as well as for SMG-dependent destabilization. Although the Hsp83 mRNA is translated in the early embryo, we show that translation of the mRNA is not necessary for destabilization; indeed, the HIE functions even when located in an mRNA's 3' untranslated region. The Hsp83 mRNA contains eight predicted SMG recognition elements (SREs); all map to the ORF, and six reside within the HIE. Mutation of a single amino acid residue that is essential for SMG's interaction with SREs stabilizes endogenous Hsp83 transcripts. Furthermore, simultaneous mutation of all eight predicted SREs also results in transcript stabilization. A plausible model is that the multiple, widely distributed SREs in the ORF enable some SMG molecules to remain bound to the mRNA despite ribosome transit through any individual SRE. Thus, SMG can recruit the CCR4-NOT deadenylase to trigger Hsp83 mRNA degradation despite the fact that it is being translated.

Regulation and function of maternal mRNA destabilization during early Drosophila development.

Early embryonic development in all animals depends on maternally provided gene products. Posttranscriptional and posttranslational processes control spatial and temporal readout of the maternal information. This review focuses on the control of maternal transcript stability in the early Drosophila embryo and how transcript destabilization is necessary for normal development. The molecular pathways that regulate transcript stability are often intimately linked with other posttranscriptional mechanisms such as mRNA localization and translational regulation. These additional mechanisms are explored here with an emphasis on their relationship to transcript decay.

Smaug recruits the CCR4/POP2/NOT deadenylase complex to trigger maternal transcript localization in the early Drosophila embryo.

BACKGROUND: Asymmetric localization of mRNAs within cells promotes precise spatio-temporal control of protein synthesis. Although cytoskeletal transport-based localization during Drosophila oogenesis is well characterized, little is known about the mechanisms that operate to localize maternal RNAs in the early embryo. One such mechanism-termed "degradation/protection"-acts on maternal Hsp83 transcripts, removing them from the bulk cytoplasm while protecting them in the posterior pole plasm. RESULTS: Here, we identify the RNA binding protein, Smaug, previously known as a translational repressor of nanos, as a key regulator of degradation/protection-based transcript localization. In smaug mutants, degradation of Hsp83 transcripts is not triggered, and, thus, localization does not occur. Hsp83 transcripts are in an mRNP complex containing Smaug, but Smaug does not translationally repress Hsp83 mRNA. Rather, Smaug physically interacts with the CCR4/POP2/NOT deadenylase, recruiting it to Hsp83 mRNA to trigger transcript deadenylation and degradation. When Smaug is targeted to heterologous stable reporter transcripts in vivo, these are deadenylated and destabilized. A deletion that removes the gene encoding CCR4 exhibits dose-sensitive interactions with Smaug in both a loss-of-function and a gain-of-function context. Reduction of CCR4 protein levels compromises Hsp83 transcript destabilization. CONCLUSIONS: Smaug triggers destabilization and localization of specific maternal transcripts through recruitment of the CCR4/POP2/NOT deadenylase. In contrast, Smaug-mediated translational repression is accomplished via an indirect interaction between Smaug and eIF4E, a component of the basic translation machinery. Thus, Smaug is a multifunctional posttranscriptional regulator that employs distinct mechanisms to repress translation and to induce degradation of target transcripts.

Regulation of maternal transcript destabilization during egg activation in Drosophila.

In animals, the transfer of developmental control from maternal RNAs and proteins to zygotically derived products occurs at the midblastula transition. This is accompanied by the destabilization of a subset of maternal transcripts. In Drosophila, maternal transcript destabilization occurs in the absence of fertilization and requires specific cis-acting instability elements. We show here that egg activation is necessary and sufficient to trigger transcript destabilization. We have identified 13 maternal-effect lethal loci that, when mutated, result in failure of maternal transcript degradation. All mutants identified are defective in one or more additional processes associated with egg activation. These include vitelline membrane reorganization, cortical microtubule depolymerization, translation of maternal mRNA, completion of meiosis, and chromosome condensation (the S-to-M transition) after meiosis. The least pleiotropic class of transcript destabilization mutants consists of three genes: pan gu, plutonium, and giant nuclei. These three genes regulate the S-to-M transition at the end of meiosis and are thought to be required for the maintenance of cyclin-dependent kinase (CDK) activity during this cell cycle transition. Consistent with a possible functional connection between this S-to-M transition and transcript destabilization, we show that in vitro-activated eggs, which exhibit aberrant postmeiotic chromosome condensation, fail to initiate transcript degradation. Several genetic tests exclude the possibility that reduction of CDK/cyclin complex activity per se is responsible for the failure to trigger transcript destabilization in these mutants. We propose that the trigger for transcript destabilization occurs coincidently with the S-to-M transition at the end of meiosis and that pan gu, plutonium, and giant nuclei regulate maternal transcript destabilization independent of their role in cell cycle regulation.