Repetitive Domain Research Articles

Evaluation of the ADOS Revised Algorithm: The Applicability in 558 Dutch Children and Adolescents

The revised ADOS algorithms, proposed by Gotham et al. (J Autism Dev Disord 37:613–627, 2007), were investigated in an independent sample of 558 Dutch children (modules 1, 2 and 3). The revised algorithms lead to better balanced sensitivity and specificity for modules 2 and 3, without losing efficiency of the classification. Including the restricted repetitive behaviour domain in the algorithm contributes to a clinical ASD classification in modules 2 and 3. For module 1, the results indicate less improvement, probably due to the low-functioning population. In most groups, the advantages of the revised algorithms are achieved without losing the strength of the original algorithm.

The γ-gliadin multigene family in common wheat (Triticum aestivum) and its closely related species

BackgroundThe unique properties of wheat flour primarily depend on gluten, which is the most important source of protein for human being. γ-Gliadins have been considered to be the most ancient of the wheat gluten family. The complex family structure of γ-gliadins complicates the determination of their function. Moreover, γ-gliadins contain several sets of celiac disease epitopes. However, no systematic research has been conducted yet.ResultsA total of 170 γ-gliadin genes were isolated from common wheat and its closely related species, among which 138 sequences are putatively functional. The ORF lengths of these sequences range from 678 to 1089 bp, and the repetitive region is mainly responsible for the size heterogeneity of γ-gliadins. The repeat motif P(Q/L/S/T/I/V/R/A)F(S/Y/V/Q/I/C/L)P(R/L/S/T/H/C/Y)Q1–2(P(S/L/T/A/F/H)QQ)1–2is repeated from 7 to 22 times. Sequence polymorphism and linkage disequilibrium analyses show that γ-gliadins are highly diverse. Phylogenic analyses indicate that there is no obvious discrimination between Sitopsis and Ae. tauschii at the Gli-1 loci, compared with diploid wheat. According to the number and placement of cysteine residues, we defined nine cysteine patterns and 17 subgroups. Alternatively, we classified γ-gliadins into two types based on the length of repetitive domain. Amino acid composition analyses indicate that there is a wide range of essential amino acids in γ-gliadins, and those γ-gliadins from subgroup SG-10 and SG-12 and γ-gliadins with a short repetitive domain are more nutritional. A screening of toxic epitopes shows that γ-gliadins with a pattern of C9 and γ-gliadins with a short repetitive domain almost lack any epitopes.Conclusionγ-Gliadin sequences in wheat and closely related Aegilops species are diverse. Each group/subgroup contributes differently to nutritional quality and epitope content. It is suggested that the genes with a short repetitive domain are more nutritional and valuable. Therefore, it is possible to breed wheat varieties, the γ-gliadins of which are less, even non-toxic and more nutritional.

Genetic mapping and annotation of genomic microsatellites isolated from globe artichoke

Cynara cardunculus includes three taxa, the globe artichoke (subsp. scolymus L. Hegi), the cultivated cardoon (var. altilis) and their progenitor, the wild cardoon (var. sylvestris). Globe artichoke is an important component of the Mediterranean rural economy, but its improvement through breeding has been rather limited and its genome organization remains largely unexplored. Here, we report the isolation of 61 new microsatellite loci which amplified a total of 208 alleles in a panel of 22 C. cardunculus genotypes. Of these, 51 were informative for linkage analysis and 39 were used to increase marker density in the available globe artichoke genetic maps. Sequence analysis of the 22 loci associated with genes showed that 9 are located within coding sequence, with the repetitive domain probably being involved in DNA binding or in protein-protein interactions. The expression of the genes associated with 9 of the 22 microsatellite loci was demonstrated by RT-PCR.

Identification and isolation of a new x‐type HMW glutenin subunit 1Dx1.6t gene from Aegilops tauschii

AbstractA new x‐type HMW glutenin subunit, designated as 1Dx1.6t from Aegilops tauschii was identified and characterized by SDS‐PAGE and MALDI‐TOF‐MS. This subunit is located between 1Dx2 and 1Dx1.5t and possesses a molecular mass (Mr) of 88565.8 Da. Its complete coding sequence was amplified via allele‐specific PCR (AS‐PCR), and the amplified product was cloned and sequenced. The authenticity of the cloned 1Dx1.6t gene was confirmed by successful expression of its open reading frame in Escherichia coli. The molecular characterization of 1Dx1.6t gene showed that its coding region consisted of 2541 bp encoding a polypeptide of 845 amino acid residues. Sequence comparison to previously characterized 1Dx1.5t subunit which is related to good dough quality of bread wheat indicated that the 1Dx1.6t subunit displayed high homology, but possesses 14 residue substitutions and a nonapeptide insertion. A total of 12 single‐nucleotide polymorphisms (1 per 212 bp) was identified in the 1Dx1.6t allele (11 in repetitive domain and 1 in the C‐terminal domain), which could facilitate the design of AS‐PCR markers.

Regression of language and non‐language skills in pervasive developmental disorders

As part of the pervasive developmental disorders (PDD), there is a subgroup of individuals reported to have a different onset of symptom appearance consisting of an apparently normal early development, followed by a loss of verbal and/or non-verbal skills prior to 2 years of age. This study aims at comparing the symptomatology of children who displayed a regression and often an associated intellectual disability through investigation of two types of loss, namely language and other skill regression. This study examined the occurrence of regression in 135 children with PDD, mean age 6.3 years. The sample was composed of 80 (59.4%) children diagnosed with autism, 44 (32.6%) with pervasive developmental disorder-not otherwise specified (PDD-NOS) and 11 (8%) with Asperger syndrome. The Autism Diagnostic Interview Revised (ADI-R) was used to evaluate the type of loss and to characterise associated factors including birth rank, gender and thimerosal exposure through vaccination. A total of 30 (22%) subjects regressed: nine (30%) underwent language regression alone, 17 (57%) lost a skill other than language and four (13%) lost both language and another skill. Significantly higher levels of regression were found in autism (30%) compared with PDD-NOS (14%) and Asperger syndrome (0%). Children who regressed in language skills spoke at a significantly earlier age ( = 12 months) than those who did not regress in this domain ( = 26 months). Parents and interviewers consistently reported developmental abnormalities prior to the loss. ADI-R domain mean scores indicated a more severe autistic symptomatology profile in children who regressed compared with those who did not, especially in the repetitive behaviour domain. Regression was not associated to thimerosal exposure, indirectly estimated by year of birth. A loss of skill, present in one out of five children with PDD, is associated with a slightly more severe symptomatology as measured by the ADI-R, particularly in the repetitive behaviours domain. Furthermore, although abnormalities are often noticed by the caregivers at the time of regression, the ADI-R reveals that other atypical behaviours were in fact present prior to the onset of regression in most cases. None of the secondary factors investigated were associated with regression. In children unexposed to thimerosal-containing vaccines, the rate of regression was similar to that reported in studies of samples exposed to thimerosal, suggesting that thimerosal has no specific association with regressive autism.

Differences in the clinical presentation of Trisomy 21 with and without autism

Autism occurs 10 times more often in children with Down syndrome than in the general population, but diagnosing co-occurring autism in Down syndrome with severe intellectual disability is challenging. The objective of this case-control study was to identify characteristics differentiating children with trisomy 21 with and without autism and to determine the extent to which severe cognitive impairment affects the measures of autism symptomatology. Twenty children with trisomy 21 and autism (cases) were compared with children with trisomy 21 without autism (controls) matched on chronologic age, race and gender. Communication, cognitive and adaptive behaviour skills were assessed with standardized instruments. Medical history was reviewed and medical records were examined for early head growth. Scores on the diagnostic algorithm of the Autism Diagnostic Interview--Revised (ADI-R) were compared after adjusting for cognitive ability as measured by the Stanford-Binet (Fifth Edition) non-verbal change sensitive score. Cases performed significantly more poorly on all assessments. Mean case-control differences for matched pairs were all significant at P < 0.0001 for receptive and expressive language skills, cognitive skills and adaptive skills. Seven cases had a history of seizures compared with one control(P = 0.01). After adjusting for cognitive ability, the mean scores on the Reciprocal Social Interaction, Communication, and Restricted, Repetitive and Stereotyped Behaviours domains of the ADI-R diagnostic algorithm remained significantly higher in cases compared with controls (P < 0.0001). All participants had decreased head size consistent with Down syndrome, with no case-control differences. Children with trisomy 21 and autism have significantly more impaired brain function than children with trisomy 21 without autism. However, the deficits in the core domains of social reciprocity and communication, and the restricted and repetitive interests are not entirely explained by the more severe cognitive impairment. This autism phenotype in children with trisomy 21 which includes an increased risk for seizures may indicate a widespread loss of functional connectivity in the brain.

Molecular evolution of dentin phosphoprotein among toothed and toothless animals

BackgroundDentin sialophosphoprotein (DSPP) is the largest member of the SIBLING family and is the most abundant noncollagenous protein in dentin. DSPP is also expressed in non-mineralized tissues including metabolically active ductal epithelia and some cancers. Its function, however, is poorly defined. The carboxy-terminal fragment, dentin phosphoprotein (DPP) is encoded predominantly by a large repetitive domain that requires separate cloning/sequencing reactions and is, therefore, often incomplete in genomic databases. Comparison of DPP sequences from at least one member of each major branch in the mammalian evolutionary tree (including some "toothless" mammals) as well as one reptile and bird may help delineate its possible functions in both dentin and ductal epithelia.ResultsThe BMP1-cleavage and translation-termination domains were sufficiently conserved to permit amplification/cloning/sequencing of most species' DPP. While the integrin-binding domain, RGD, was present in about half of species, only vestigial remnants of this tripeptide were identified in the others. The number of tandem repeats of the nominal SerSerAsp phosphorylation motif in toothed mammals (including baleen whale and platypus which lack teeth as adults), ranged from ~75 (elephant) to >230 (human). These repeats were not perfect, however, and patterns of intervening sequences highlight the rapidity of changes among even closely related species. Two toothless anteater species have evolved different sets of nonsense mutations shortly after their BMP1 motifs suggesting that while cleavage may be important for DSPP processing in other tissues, the DPP domain itself may be required only in dentin. The lizard DSPP had an intact BMP1 site, a remnant RGD motif, as well as a distinctly different Ser/Asp-rich domain compared to mammals.ConclusionsThe DPP domain of DSPP was found to change dramatically within mammals and was lost in two truly toothless animals. The defining aspect of DPP, the long repeating phosphorylation domain, apparently undergoes frequent slip replication and recombination events that rapidly change specific patterns but not its overall biochemical character in toothed animals. Species may have to co-evolve protein processing mechanisms, however, to handle increased lengths of DSP repeats. While the RGD domain is lost in many species, some evolutionary pressure to maintain integrin binding can be observed.

Molecular characterization of LMW-GS genes from a somatic hybrid introgression line II-12 between Triticum aestivum and Agropyron elongatum in relation to quick evolution

In order to exploit the evolution and find novel low-molecular-weight glutenin subunit (LMW-GS) for improvement of common wheat quality, thirteen variants from a somatic hybrid introgression line II-12 between Triticum aestivum cv. Jinan 177 (JN177) and Agropyron elongatum were characterized via genomic PCR. Four clones were pseudogenes because they contained an internal stop codon. The remaining nine variants contained intact open reading frames (ORFs). Sequence alignment indicates that the proteins deduced from the nine ORFs have similar primary structure with LMW-GS cloned from its parents previously. However, they have some unique modifications in the structures. For example, EU292737 contains not only an extra Cys residue in the C-terminal domain but also a long repetitive domain. Both EU159511 and EU292738 start their first Cys residue in the N-terminal repetitive domain, but not in the N-conserved domain traditionally. These structural alterations may have positive contributions to wheat flour quality. The results of phylogeny showed that most LMW-GS variances from II-12 were homologous to those from parent JN177 and other wheat lines. The reason for quick evolution of LMW-GS in II-12 was discussed.

Tracing misalignment and unequal crossing over during evolution of the repetitive region of the SM50 gene in sea urchins

The location of misalignment and unequal crossover involved in concerted evolution of tandemly repetitive sequences is difficult to document owing to the homogeneity of sequences that are subject to this process. However, the repetitive domain of the SM50 gene in sea urchins contains variation, within the gene itself, between alleles, and between species that has allowed us to determine where misalignment and unequal crossing over occurred during evolution of this gene. We have therefore analyzed the SM50 repeat regions in a variety of species to determine where recent changes in repeat numbers have occurred, and from this have deduced the mechanisms that lead to these changes. We next tried to determine whether recent misalignment and unequal crossover has produced allelic variation in current populations of sea urchins. We found SM50 alleles within three species that have different numbers of repeats. This marks the first reported documentation of allelic variation in the number of repeats in the SM50 gene. We also show how a single unequal crossover event could have produced the allelic variation. We have found that substitutions and small deletions in the sequences within the repeats can substantially affect how misalignment occurs, resulting in different patterns of repeats after concerted evolution.

Isolation and characterization of a novel HMW-GSGlu-Dxallele from Tibet bread wheat landrace

A novel HMW-GS of Dx5** with slightly faster migration rate than that of Dx5, was found in a Tibet bread wheat landrace using SDS-PAGE. Moreover, Dx5** is the subunit with the fastest migration rate in Glu-Dx locus. The gene for this subunit was isolated and its sequence was obtained in the present study. This gene was very similar to Dx5 both in nucleotide and deduced amino acid sequence. At the nucleotide sequence level, Dx5** different from Dx5 by the deletion of a 27 bp fragment and two nucleotide replacements at position 353(G/C) and 692(C/G), respectively. At the amino acid sequence level, Dx5** different from Dx5 by the deletion of a hexaploid (LGQGQQ) and a tripeptide (GQQ) repetitive motif and two amino acid replacements at position 118(C/S) and 231(A/G), respectively. These results suggested that the Dx5** was a derivation of Dx5 and was formed by replication slippage. Moreover, the specific cysteine (C) located at the beginning of the repetitive domain of Dx5, which proved to be critical for the end-use quality of wheat flours, was replaced by serine (S) in Dx5**.

Role of Protein Translocation Pathways across the Endoplasmic Reticulum in Trypanosoma brucei

The translocation of secretory and membrane proteins across the endoplasmic reticulum (ER) membrane is mediated by co-translational (via the signal recognition particle (SRP)) and post-translational mechanisms. In this study, we investigated the relative contributions of these two pathways in trypanosomes. A homologue of SEC71, which functions in the post-translocation chaperone pathway in yeast, was identified and silenced by RNA interference. This factor is essential for parasite viability. In SEC71-silenced cells, signal peptide (SP)-containing proteins traversed the ER, but several were mislocalized, whereas polytopic membrane protein biogenesis was unaffected. Surprisingly trypanosomes can interchangeably utilize two of the pathways to translocate SP-containing proteins except for glycosylphosphatidylinositol-anchored proteins, whose level was reduced in SEC71-silenced cells but not in cells depleted for SRP68, an SRP-binding protein. Entry of SP-containing proteins to the ER was significantly blocked only in cells co-silenced for the two translocation pathways (SEC71 and SRP68). SEC63, a factor essential for both translocation pathways in yeast, was identified and silenced by RNA interference. SEC63 silencing affected entry to the ER of both SP-containing proteins and polytopic membrane proteins, suggesting that, as in yeast, this factor is essential for both translocation pathways in vivo. This study suggests that, unlike bacteria or other eukaryotes, trypanosomes are generally promiscuous in their choice of mechanism for translocating SP-containing proteins to the ER, although the SRP-independent pathway is favored for glycosylphosphatidylinositol-anchored proteins, which are the most abundant surface proteins in these parasites.

Clinical potential of mucins in diagnosis, prognosis, and therapy of ovarian cancer

Knowledge of mucins and their multiple roles in various normal and pathological processes has improved greatly in the past two decades. Mucins belong to a family of glycoproteins characterised by densely O-glycosylated repetitive domains and expressed by various surface epithelial cells. Altered expression of mucins is present in various diseases, including cancer. Ovarian cancer is the sixth most common cancer worldwide and the seventh leading cause of cancer-related deaths in women. The most common ovarian cancer is epithelial ovarian carcinoma, which is characterised by few early symptoms, widespread peritoneal dissemination, and ascites at advanced stages that result in poor prognosis. After diagnosis, 5 year survival is only 35-45%. Therefore, improved strategies for early diagnosis and treatment are needed. Because of the surface epithelial origin of epithelial ovarian cancer, mucins are obvious biomolecules for investigation as markers for early diagnosis and as therapeutic targets. We discuss the potential role and clinical usefulness of mucins in early diagnosis, prognosis, and treatment of ovarian cancer.

Symptoms and Behavior Problems of Adolescents and Adults With Autism: Effects of Mother–Child Relationship Quality, Warmth, and Praise

Using a cross-lagged panel design, we investigated the impact of positive family processes on change in autism symptoms and behaviors. A sample of 149 co-residing mothers and their adolescent or adult child with autism was drawn from a large, longitudinal study. Maternal warmth and praise were measured using coded speech samples in which mothers talked about their son or daughter. A high level of relationship quality was associated with subsequent reductions in internalizing and externalizing problems as well as reductions in impairments in social reciprocity and repetitive behaviors. Maternal warmth and praise were also related to symptom abatement in the repetitive behaviors domain.

Molecular characterization of LMW prolamines from Crithopsis delileana and the comparative analysis with those from Triticeae

Using the homologous primers designed from known sequences of low-molecular-weight glutenin subunits (LMW-GS), four LMW prolamine gene sequences, designated as LMW-GSK1 (EU283813), LMW-GSK2 (EU283814), LMW-GSK3 (EU283815) and LMW-GSK4 (EU283816), were isolated from wheat-related diploid species Crithopsis delileana, among which LMW-GSK3 and LMW-GSK4 were partial gene sequences. These LMW prolamine gene sequences from C. delileana had the similar typical primary structures to the known LMW glutenin subunit genes in wheat and its related species. The 5′ flanking region of the LMW-GSK1 contained two cis-elements EM (5′-TGTAAAGT-3′) and GLM (5′-GGCGAGTCAT-3′). The deduced amino-acid sequence of the LMW-GSK1 consisted of a conserved signal peptide with 20 residues, a N-terminal region with 15 residues, a repetitive domain with 80 residues and a C-terminal region with 182 residues. Several in-frame stop codons were found in the coding sequences of LMW-GSK2 and LMW-GSK4, indicating that the LMW-GSK2 and LMW-GSK4 could be the putative pseudogenes. Phylogenetic analysis indicated that LMW-GSK1, LMW-GSK2 and LMW-GSK4 were closely related to the LMW-GS genes from A, D and R genomes, while LMW-GSK3 could be clustered together with X03103 from H genome. It was the first time that the coding genes of LMW prolamines on K genome of C. delileana were characterized.

Cooperation ofSalmonellapathogenicity islands 1 and 4 is required to breach epithelial barriers

Invasion is an important microbial virulence strategy to overcome the barrier formed by polarized epithelial cells. Salmonella enterica is a food-borne pathogen that deploys a type III secretion system for the manipulation of the actin cytoskeleton and to trigger internalization into epithelial cells. Here we show that this function is not sufficient to enter polarized cells and report that penetration of epithelia from the luminal side requires both the type III secretion system and novel virulence functions conferred by Salmonella pathogenicity island 4. Salmonella pathogenicity island 4 encodes a type I secretion system for the giant non-fimbrial adhesin SiiE that mediates intimate contact of Salmonella to microvilli on the apical membrane. Mutant strains lacking SiiE fail to invade polarized cells, to destroy epithelial barrier functions and to efface the apical brush border. Deletion analyses of repetitive domains in SiiE indicate that the large size of the adhesin is of functional importance. Our observations demonstrate that efficient penetration of epithelial barriers requires the cooperative activity of two Salmonella pathogenicity islands encoding different secretion systems. These findings underline the role of the epithelial brush border and reveal a new mechanism used by bacterial pathogens to overcome this barrier.

Characterization of Ccw7p cell wall proteins and the encoding genes ofSaccharomyces cerevisiaewine yeast strains: relevance for flor formation

The specific flavour of Sherry-type wines requires aromatic compounds produced as by-products of the oxidative metabolism of yeasts that are able to form a biofilm (flor) at the wine surface. A similar yeast pellicle develops on the surface of 'Tokaji Szamorodni', one of the traditional Hungarian botrytized wines, during maturation. In this work, patterns of biotinylated cell wall proteins extracted from film-forming and nonfilm-forming Saccharomyces cerevisiae strains were compared. It was found that all the tested 23 film-forming 'Szamorodni' yeast strains had a decreased size of the Ccw7/Hsp150 protein, one of the members of the Pir-protein family. Sequencing of the encoding genes revealed that the strains were lacking three out of the 11 repeating sequences characteristic to this protein family. One of the film-forming strains contained CCW7 alleles of different length, which was generated by intragenic tandem duplication of a sequence containing two repetitive domains. Unlike the film-forming strains, 16 nonfilm-forming wine yeasts isolated from a different botrytized wine, 'Tokaji Aszu', showed pronounced polymorphism of the CCW7 locus. It is highly probable that the modified Ccw7 protein does not contribute to the increased hydrophobicity of film-forming strains but it may influence molecular reorganization of the cell wall during stress adaptation.

Cloning and molecular characterization of a novel x-type glutenin gene Glu-D t 1 from Aegilops tauschii

A novel gene encoding an x-type high molecular weight glutenin subunit (HMW-GS), designated 1Dx1.1(t), was isolated from Aegilops tauschii. It is the largest HMW-GS gene reported so far in this species and its product has a slower mobility than that of subunit 1Ax1 in SDS-PAGE. The open reading frame (ORF) of the gene was 2,628 bp, encoding a protein of 874 amino acid residues. Comparisons of amino acid sequences showed that subunit 1Dx1.1(t) had high similarity with other 1Dx subunits but also had two unique characteristics. Firstly, a tripeptide of consensus LQE present in the N-terminal domains of other 1Dx subunits was absent from subunit Dx1.1(t). Secondly, three copies of tandem duplications of the tripeptide motif GQQ and a novel tripeptide sequence (GQL) were present in its central repetitive domain. Phylogenetic analysis showed that subunit 1Dx1.1(t) clustered with other known 1Dx subunits.

Isolation and characterization of a low molecular weight glutenin gene from &lt;I&gt;Taenitherum&lt;/I&gt; Nevski

More and more low-molecular-weight glutenin(LMW glutenin) genes were isolated and characterized from hexaploid wheat (Triticum aestivum L.). However, few homologous genes were obtained from its relative species, which limited our understanding of the relationships among them. Therefore, it is necessary to isolate LMW glutenin homologous genes from wheat wild relative species. Using a pair of specific oligonucleotide PCR primers for Taenitherum genomic DNA, a LMW glutenin gene sequence, with nucleotide sequence in 1 035 bp and deduced amino acid sequence with 343 amino acid residues, was obtained. This sequence was a typical LMW glutenin sequence and characterized by a signal peptide of 21 amino acid residues, a N-terminal conservative domain of 13 amino acid residues, a repetitive domain of short peptide, and a C-terminal conservative domain. Sequence alignment showed the main differences and the relationships between LMW glutenin genes from wheat and Taenitherum. The results presented here give a reference to isolate LMW glutenin gene from Taenitherum, as well as other wheat wild relatives.

Molecular cloning and characterization of four novel LMW glutenin subunit genes from Aegilops longissima, Triticum dicoccoides and T. zhukovskyi

This paper reports cloning and characterisation of four novel low-molecular-weight glutenin subunit (LMW-GS) genes (designated as TzLMW-m2, TzLMW-m1, TdLMW-m1 and AlLMW-m2) from the genomic DNA of Triticum dicoccoides, T. zhukovskyi and Aegilops longissima. The coding regions of TzLMW-m2, TzLMW-m1, TdLMW-m1 and AlLMW-m2 were 1056 bp, 903 bp, 1056 bp and 1050 bp in length, encoding 350, 300, 350 and 348 amino acid residues, respectively. The deduced amino acid sequences showed that the four novel genes were classified as LMW-m types and the comparison results indicated that the four genes had a more similar structure and a higher level of homology with the LMW-m genes than the LMW-s and -i types genes. However, the first cysteine residue's positions of TzLMW-m2, TdLMW-m1 and AlLMW-m2 were different from the others. Moreover, AlLMW-m2, TdLMW-m1 and TzLMW-m2 all possessed a longer repetitive domain, which was considered to be associated with good quality of wheat. The secondary structure prediction revealed that the content of beta-strand in AlLMW-m2 and TdLMW-m1 exceeded the positive control, suggesting that AlLMW-m2 and TdLMW-m1 should be considered as candidate genes that may have positive effect on dough quality. In order to investigate the evolutionary relationship of the novel genes with the other LMW-GSs, a phylogenetic tree was constructed. The results lead to a speculation that AlLMW-m2, TdLMW-m1 and TzLMW-m2 may be the middle types during the evolution of LMW-m and LMW-s.

Drosophila Ankyrin 2 Is Required for Synaptic Stability

Synaptic connections are stabilized through transsynaptic adhesion complexes that are anchored in the underlying cytoskeleton. The Drosophila neuromuscular junction (NMJs) serves as a model system to unravel genes required for the structural remodeling of synapses. In a mutagenesis screen for regulators of synaptic stability, we recovered mutations in Drosophila ankyrin 2 (ank2) affecting two giant Ank2 isoforms that are specifically expressed in the nervous system and associate with the presynaptic membrane cytoskeleton. ank2 mutant larvae show severe deficits in the stability of NMJs, resulting in a reduction in overall terminal size, withdrawal of synaptic boutons, and disassembly of presynaptic active zones. In addition, lack of Ank2 leads to disintegration of the synaptic microtubule cytoskeleton. Microtubules and microtubule-associated proteins fail to extend into distant boutons. Interestingly, Ank2 functions downstream of spectrin in the anchorage of synaptic microtubules, providing the cytoskeletal scaffold that is essential for synaptic stability.