Paracrystalline Inclusions Research Articles

Multi-level profiling unravels mitochondrial dysfunction in myotonic dystrophy type 2

Myotonic dystrophy type 2 (DM2) is an autosomal-dominant multisystemic disease with a core manifestation of proximal muscle weakness, muscle atrophy, myotonia, and myalgia. The disease-causing CCTG tetranucleotide expansion within the CNBP gene on chromosome 3 leads to an RNA-dominated spliceopathy, which is currently untreatable. Research exploring the pathophysiological mechanisms in myotonic dystrophy type 1 has resulted in new insights into disease mechanisms and identified mitochondrial dysfunction as a promising therapeutic target. It remains unclear whether similar mechanisms underlie DM2 and, if so, whether these might also serve as potential therapeutic targets. In this cross-sectional study, we studied DM2 skeletal muscle biopsy specimens on proteomic, molecular, and morphological, including ultrastructural levels in two separate patient cohorts consisting of 8 (explorative cohort) and 40 (confirmatory cohort) patients. Seven muscle biopsy specimens from four female and three male DM2 patients underwent proteomic analysis and respiratory chain enzymology. We performed bulk RNA sequencing, immunoblotting of respiratory chain complexes, mitochondrial DNA copy number determination, and long-range PCR (LR-PCR) to study mitochondrial DNA deletions on six biopsies. Proteomic and transcriptomic analyses revealed a downregulation of essential mitochondrial proteins and their respective RNA transcripts, namely of subunits of respiratory chain complexes I, III, and IV (e.g., mt-CO1, mt-ND1, mt-CYB, NDUFB6) and associated translation factors (TACO1). Light microscopy showed mitochondrial abnormalities (e.g., an age-inappropriate amount of COX-deficient fibers, subsarcolemmal accumulation) in most biopsy specimens. Electron microscopy revealed widespread ultrastructural mitochondrial abnormalities, including dysmorphic mitochondria with paracrystalline inclusions. Immunofluorescence studies with co-localization of autophagy (p62, LC-3) and mitochondrial marker proteins (TOM20, COX-IV), as well as immunohistochemistry for mitophagy marker BNIP3 indicated impaired mitophagic flux. Immunoblotting and LR-PCR did not reveal significant differences between patients and controls. In contrast, mtDNA copy number measurement showed a reduction of mtDNA copy numbers in the patient group compared to controls. This first multi-level study of DM2 unravels thus far undescribed functional and structural mitochondrial abnormalities. However, the molecular link between the tetranucleotide expansion and mitochondrial dysfunction needs to be further elucidated.

Mitochondrial encephalomyopathy with lactic acidosis and stroke-like episodes syndrome: a case report

ABSTRACT A biopsy of gastrocnemius muscle from a patient with mitochondrial encephalomyopathy with lactic acidosis and stroke-like episodes (MELAS) syndrome was studied histologically in semithin sections stained by hematoxylin-and-eosin (H&E) and toluidine blue, and ultrathin sections by transmission electron microscopy (TEM). H&E stain demonstrated typical ragged-red fibers (RRFs) and affected fibers in fascicles. Toluidine-blue stain showed an irregular meshwork in the center of RRFs. TEM demonstrated damaged myofibrils and variations in mitochondrial structure in RRFs and affected fibers. Dense mitochondria were compacted with cristae and pleomorphic electron-dense inclusions. Lucent mitochondria included paracrystalline inclusions with a parking lot appearance. At high magnification, the paracrystalline inclusions were composed of plates that paralleled and connected with mitochondrial cristae. These observations indicated that electron-dense granular and paracrystalline inclusions resulted from cristal degeneration and overlapping in mitochondria in MELAS syndrome.

The new chytridiomycete Paradinomyces triforaminorum gen. et sp. nov. co-occurs with other parasitoids during a Kryptoperidinium foliaceum (Dinophyceae) bloom in the Baltic Sea

A new chytrid genus and species was isolated and cultured from samples obtained in the Baltic Sea during a dinoflagellate bloom event. This species is characterized by having a spherical sporangium without papillae and zoospores of 2–3 µm in diameter that are released through 3 discharge pores. Molecular phylogeny based on ribosomal operon showed its sister position to the Dinomyces cluster in Rhizophydiales. Zoospores lack fenestrated cisternae but contain a paracrystalline inclusion, found in a Rhizophydiales representative for the first time. Additionally, the kinetid features are uncommon for Rhizophydiales and only observed in Dinomyces representatives so far. These morphological features and its phylogenetic relationships justify the description of the new genus and speciesParadinomyces triforaminorum gen. nov. sp. nov. belonging to the family Dinomycetaceae. The chytrid was detected during a high-biomass bloom of the dinoflagellate Kryptoperidinium foliaceum. Laboratory experiments suggest this species is highly specific and demonstrate the impact it can have on HAB development. The chytrid co-occurred with three other parasites belonging to Chytridiomycota (Fungi) and Perkinsea (Alveolata), highlighting that parasitic interactions are common during HABs in brackish and marine systems, and these multiple parasites compete for similar hosts.

Abstract 10557: A Case of Cardiogenic Shock in a Woman With a Mitochondrial Cardiomyopathy

Case Presentation: A 35-year-old woman with nonischemic cardiomyopathy, with a left ventricular ejection fraction <20% on home dobutamine, and chronic weakness was referred to our institution for heart transplantation evaluation. She was directly admitted to the hospital for suspected cardiogenic shock after her labs revealed a lactate level of 5.4 mmol/L. Her hospital course was complicated by persistently undulating lactate levels (0.2 - 8.6 mmol/L) that increased with exertion, despite normal mixed venous oxygen saturation measurements obtained from a pulmonary artery catheter. Serologic genetic testing was negative, and electromyography revealed the presence of a proximal and axial myopathy. A deltoid muscle biopsy was obtained, and genetic testing of the specimen revealed two mitochondrial deoxyribonucleic acid deletions, and electron microscopy revealed mitochondrial paracrystalline inclusions. She subsequently underwent left ventricular assist device placement and was started on carnitine, arginine, creatine, thiamine, and coenzyme Q10 supplementation. Despite left ventricular assist device placement, the patient has continued to decline due to progressive right heart failure and is currently being considered for cardiac transplantation. Discussion: Mitochondrial cardiomyopathy (MCM) is an alteration in cardiac structure and function caused by genetic defects of the mitochondrial respiratory chain, in the absence of other causes of heart failure. The true prevalence of MCM is unknown. Clinical manifestations in those with MCM present on a spectrum, ranging from asymptomatic cases to those with signs and symptoms typical of heart failure. Extra-cardiac features commonly include chronic weakness and fatigue. Diagnosis is made with prompt genetic testing and microscopic evaluation of a skeletal muscle biopsy specimen. Outcomes in patients who receive a left ventricular assist device are unknown and warrant further investigation.

Reinke crystals: Hallmarks of adult Leydig cells in humans.

Reinke crystals are structures pathognomonic for Leydig cells, which have the important function of testosterone production and are vital for male reproductive health. These crystalline inclusions are thought to be of protein origin; however, the molecular composition has not yet been resolved. This review summarizes all available information regarding Reinke crystal's characteristics and aims to produce a comprehensive guide for research on this topic as well as to determine and discuss potential Reinke-protein candidates. Pubmed was thoroughly searched for all publications regarding Reinke crystals and 137 publications were identified. All publications were surveyed and all relevant information was included in the review. Along with the cytoplasm, structures that resemble Reinke crystals were also observed in the nucleus, suggesting that their formation depends only on protein concentration. Variations in tissue processing protocols could impact Reinke crystal microscopic visualization, which is an important factor in diagnosing Leydig cell disorders such as Leydig cell tumors. Reinke crystals appear to be hallmarks of normally differentiated, adult, Leydig or Leydig-like cells in humans, while some abnormal and nonhuman Leydig cells contain Reinke-like paracrystalline inclusions or crystalloids. These characteristics point to some differentially expressed proteins, which could be involved in Reinke crystal formation. Differential Reinke crystal and paracrystalline inclusion presence could also be due to small changes in protein structure or the cell environment. Further research is needed to solve the ongoing mystery of the Reinke crystal, which would enhance our knowledge of Leydig cell contribution in the pathogenesis of various male reproductive disorders and improve their diagnosis and treatment.

Novel Mutation m.10372A>G in MT-ND3 Causing Sensorimotor Axonal Polyneuropathy.

ObjectiveTo investigate the pathogenicity of a novel MT-ND3 mutation identified in a patient with adult-onset sensorimotor axonal polyneuropathy and report the clinical, morphologic, and biochemical findings.MethodsClinical assessments and morphologic and biochemical investigations of skeletal muscle and cultured myoblasts from the patient were performed. Whole-genome sequencing (WGS) of DNA from skeletal muscle and Sanger sequencing of mitochondrial DNA (mtDNA) from both skeletal muscle and cultured myoblasts were performed. Heteroplasmic levels of mutated mtDNA in different tissues were quantified by last-cycle hot PCR.ResultsMuscle showed ragged red fibers, paracrystalline inclusions, a significant reduction in complex I (CI) respiratory chain (RC) activity, and decreased adenosine triphosphate (ATP) production for all substrates used by CI. Sanger sequencing of DNA from skeletal muscle detected a unique previously unreported heteroplasmic mutation in mtDNA encoded MT-ND3, coding for a subunit in CI. WGS confirmed the mtDNA mutation but did not detect any other mutation explaining the disease. Cultured myoblasts, however, did not carry the mutation, and RC activity measurements in myoblasts were normal.ConclusionsWe report a case with adult-onset sensorimotor axonal polyneuropathy caused by a novel mtDNA mutation in MT-ND3. Loss of heteroplasmy in blood, cultured fibroblasts and myoblasts from the patient, and normal measurement of RC activity of the myoblasts support pathogenicity of the mutation. These findings highlight the importance of mitochondrial investigations in patients presenting with seemingly idiopathic polyneuropathy, especially if muscle also is affected.

The kinetid structure of two oscarellid sponges (Class Homoscleromorpha) unveils plesiomorphies in kinetids of Homoscleromorpha–Calcarea lineage

AbstractThe structure of the kinetid (flagellar or ciliary apparatus) is known to be of phylogenetic significance in sponges (Phylum Porifera) and can provide information about evolutionary relationships. Here, we report on the larval kinetid structure of two closely related species, Oscarella lobularis and O. tuberculata (Homoscleromorpha, Oscarellidae). Cells belonging to the four previously recognized morphological regions (anterior pole, lateral zone, paracrystalline belt, and posterior pole) were studied. The cells of the paracrystalline belt have pear‐shaped nuclei with a paracrystalline inclusion connected to the roots of the kinetid. In the cells of other zones, the nucleus is separated from the kinetid, and the roots adjoined the Golgi apparatus only. In kinetids of the studied larval cells, we observed the accessory centriole arranged immediately under the kinetosome, and two unequal fibrillar roots. These features are unique for sponge larvae. Comparing kinetids of the Homoscleromorpha with those in its sister group, the Calcarea, we propose an ancestral composition for the kinetid in the lineage Calcarea + Homoscleromorpha. This proposed kinetid structure includes a kinetosome–nucleus link, striated roots, simple basal foot, orthogonal centriole, and a long transition zone of the flagellum. The position of the centriole under the kinetosome in homoscleromorph larvae and the stout fibrillar or microtubular bundle on the kinetosome in calcarean larvae might be the apomorphies of these groups.

Early-onset coenzyme Q10 deficiency associated with ataxia and respiratory chain dysfunction due to novel pathogenic COQ8A variants, including a large intragenic deletion.

Coenzyme Q10 (CoQ10) deficiency is a clinically and genetically heterogeneous subtype of mitochondrial disease. We report two girls with ataxia and mitochondrial respiratory chain deficiency who were shown to have primary CoQ10 deficiency. Muscle histochemistry displayed signs of mitochondrial dysfunction—ragged red fibers, mitochondrial paracrystalline inclusions, and lipid deposits while biochemical analyses revealed complex II+III respiratory chain deficiencies. MRI brain demonstrated cerebral and cerebellar atrophy. Targeted molecular analysis identified a homozygous c.1015G>A, p.(Ala339Thr) COQ8A variant in subject 1, while subject 2 was found to harbor a single heterozygous c.1029_1030delinsCA variant predicting a p.Gln343_Val344delinsHisMet amino acid substitution. Subsequent investigations identified a large‐scale COQ8A deletion in trans to the c.1029_1030delinsCA allele. A skin biopsy facilitated cDNA studies that confirmed exon skipping in the fibroblast derived COQ8A mRNA transcript. This report expands the molecular genetic spectrum associated with COQ8A‐related mitochondrial disease and highlights the importance of thorough investigation of candidate pathogenic variants to establish phase. Rapid diagnosis is of the utmost importance as patients may benefit from therapeutic CoQ10 supplementation.

Increased intra-mitochondrial lipofuscin aggregates with spherical dense body formation in mitochondrial myopathy

Lipofuscin aggregation may result from incomplete degradation of damaged mitochondria by autophagy-lysosome pathway, and intra-mitochondrial lipofuscin aggregation may exacerbate mitochondrial abnormalities in mitochondrial myopathy (MM) and mitochondrial disease. We examined vastus lateralis muscle biopsies from 24 patients with pathologically diagnosed MM and clinically diagnosed chronic progressive external ophthalmoplegia, in comparison to the biopsies from 3 other groups:10 patients with inclusion body myositis (IBM), 11 younger adults, and 10 older subjects with no to minimal myopathic changes. Lipofuscin aggregation in muscle fibres was assessed on autofluorescence microscopy, some histochemical stains, and electron microscopy (EM). EM analyses demonstrated intra-mitochondrial lipofuscin aggregates, spherical dense bodies (SDBs), and paracrystalline inclusions (PCIs) which were semi-quantitatively assessed. Intra-mitochondrial lipofuscin aggregates showed no significant differences between groups of MM patients and older subjects or IBM patients, but significant differences between groups of younger adults and others with associated age-related changes. Intra-mitochondrial SDBs were significantly more in MM patients than in older subjects, IBM patients, and younger adults. There was a significant positive correlation between intra-mitochondrial lipofuscin aggregates and SDBs. These findings suggest that intra-mitochondrial formation of lipofuscin SDBs is more in MM and contributing to the pathophysiology of mitochondrial disease.

Ultrastructural and clinical findings of mitochondrial encephalomyopathy:report of 27 cases

Objective: To investigate the ultrastructural features of muscle in patients with mitochondrial encephalomyopathy for its diagnosis and differential diagnosis. Methods: The clinical data of 27 mitochondrial encephalomyopathy patients who underwent left or right biceps brachii muscle biopsy at Department of Neurosurgery, Beijing Tiantan Hospital, Capital Medical University from July 2006 to August 2017 were analyzed retrospectively. The muscle biopsy specimens were examined underlight microscope and transmission electron microscope. Results: There were 27 patients (17 males, 10 females) with an age range of 12 to 62 years (mean 29 years). The age of onset ranged from 3 to 38 years. The course of disease ranged from 1 month to 24 years. Twenty-two cases presented with lactic acidosis and stroke-like episodes (MELAS) syndrome, four with myoclonic epilepsy with ragged red fibers (MERRF) syndrome, and one with chronic progressive paralysis of extraocular muscle (CPEO) syndrome. Skeletal muscle biopsy showed abundant ragged red fibers and strongly SDH-reactive vessel. Genetic studies showed 17 of 22 cases of MELAS syndrome had A3243G mutation, and the other 5 cases had no abnormality. A8344G mutation was found in 3 of 4 cases of MERRF syndrome. No single or multiple mtDNA mutations were found in the single case of CPEO. Transmission electron microscopy of all 27 cases showed diffuse proliferation of mitochondria between the myofibrils and beneath the sarcolemma, with increased spacing between muscle cells. Seven cases showed numerous glycogen and four showed subsarcolemmal lipid droplets, 13 cases showed unusual mitochondrial morphology, including mitochondrial electron-dense substances and paracrystal line inclusions ("parking lot" change)in eight cases. Conclusions: Transmission electron microscopy shows significant differences in ultrastructural pathological changes among different patients with mitochondrial encephalomyopathy. Some patients with mild clinical symptoms have increased mitochondrial number, increased metabolism of glycogen and lipid droplets, while others with severe clinical symptoms have abnormal mitochondrial morphology. Typical crystalloid inclusions are found in mitochondria, which are of great value in the diagnosis of this disease.

CONGENITAL MYOPATHIES: NEMALINE AND TITINOPATHIES: P.237Congenital fatal cap-rod myopathy due to a de novo autosomal dominant pathogenic ACTA1 variant

Cap disease is a rare structural congenital myopathy (CM) associated with hypotonia, proximal and facial muscle weakness, and frequently scoliosis and respiratory involvement. Mutations in TPM2, TPM3 and ACTA1 have been associated with cap disease, as well as nemaline myopathy. Combined caps and nemaline rods have been reported in the same patient due to a mutation in TPM3. Here, we report the first case of a severe, fatal CM with distinct and separate caps and nemaline rods identified in skeletal muscle biopsies. The patient was born at 37 weeks of gestation, with a history of polyhydramnios, little spontaneous movements at birth, generalised hypotonia, and required immediate ventilatory support. He died 20 days after birth. Ante mortem and post mortem biopsies from the quadriceps, and post mortem biopsies from the biceps and diaphragm showed diffuse fibre hypotrophy without specific structural alterations on light microscopy. Ultrastructural examination of the ante mortem quadriceps biopsy showed several classical cap lesions, and a few of these contained small nemaline rods. The post mortem quadriceps sample showed nemaline rods in several fibres. Both samples showed mitochondrial paracrystalline inclusions in a few interstitial capillary endothelial cells. Ultrastructural findings were key in directing molecular genetic testing. A next generation sequencing panel for 35 congenital myopathy genes identified a de novo ACTA1 c.739G>C p.(Gly247Arg) variant previously reported in the literature in a patient with severe nemaline myopathy, affecting a highly conserved amino acid, and predicted to affect actin function with In Silico analysis. Our case of ACTA1-related cap-rod myopathy is the most severe presentation of a CM with caps or cap-rods described till date. The case further cements the notion of caps and rods being part of the 'nemaline spectrum' and highlights the remarkable heterogeneity of lesions within the same muscle or same group of muscles.

Zopfochytrium is a new genus in the Chytridiales with distinct zoospore ultrastructure

While surveying chytrid diversity in lakes and streams, we found on cellulosic bait a chytrid that had both monocentric and polycentric thallus forms. We brought this chytrid into axenic culture from three sites in eastern North America, studied its thallus development and zoospore ultrastructure, and compared its 28S rDNA sequence with those of other members of the Chytridiomycota. Thallus morphology matched that described for the rare chytrid, Cladochytrium polystomum Zopf. Sporangia were spherical and produced numerous long discharge tubes. After discharge, zoospores remained in spherical clusters at the tips of the inoperculate openings of discharge tubes. After 10–30 min zoospores either swam away or encysted in place. Zoospore ultrastructural features included a cell coat, flagellar plug, and paracrystalline inclusion, features typical of members of the Chytridiales. However, the flagellar apparatus structure and organellar organization differed from that of zoospores previously described. Based on its molecular phylogeny and its zoospore ultrastructural features, we classify C. polystomum as a member of the Chytridiaceae in the Chytridiales. Because its thallus development and its ribosomal DNA sequences diverged decidedly from those of Cladochytrium tenue Nowak, the type species of Cladochytrium, we erected Zopfochytrium as a new genus for this chytrid.

Genetic Mutations and Demographic, Clinical, and Morphological Aspects of Myofibrillar Myopathy in a French Cohort.

Protein aggregate myopathies (PAM) represent a group of familial or sporadic neuromuscular conditions with marked clinical and genetic heterogeneity that occur in children and adults. Familial PAM includes myofibrillar myopathies defined by the presence of desmin-positive protein aggregates and degenerative intermyofibrillar network changes. PAM is often caused by dysfunctional genes, such as DES, PLEC 1, CRYAB, FLNC, MYOT, ZASP, BAG3, FHL1, and DNAJB6. To retrospectively analyze genetic mutations and demographic, clinical, and morphological aspects of PAM in a French population. Forty-eight PAM patients (29 men, 19 women) were divided into two groups, those with genetically (GIM) and nongenetically identified (NGIM) mutations associated with myofibrillar myopathy. Age of myopathy onset ranged from 13 to 68 years. GIM group mutations (81.25%) included DES (14), ZASP (8), FLNC (4), MYOT (4), BAG3 (1), CRYAB (2), and DNAJB6 (6). The MYOT subgroup displayed a significantly older onset age (p = 0.029). Autosomal dominant inheritance was found in 74.3% of GIM and 44.4% of NGIM subjects. Overall, 22.9% had Maghrebian heritage, 72.9% Caucasian, and 4.2% Asian. The most common clinical sign was distal muscle weakness (66%) followed by simultaneous distal and proximal weakness in 49%. Eleven patients had contractures, one had a rigid spine, and five had respiratory dysfunction. GIM subjects had greater cardiac involvement (51.7%) versus the NGIM group (33.3%). The average serum creatine kinase level was 393 U/L in GIM and 382 U/L in NGIM subjects. Morphological analysis showed significant differences among GIM subgroups, including the number of vacuoles and regenerated fibers (ZASP), group atrophy (ZASP), and rubbed out fibers (MYOT). Ultrastructural findings showed significant differences in intranuclear rods, Z-disc thickness, and intranuclear inclusions between gene mutation subgroups. Paracrystalline inclusions were present in three patients (DNAJB6). The most frequent mutation in was in DES, followed by ZASP. GIM and NGIM PAM subjects showed similar results, suggesting that any unknown genes, which cause this disease have characteristics similar to those already described. Considering the complexity of clinical, morphological, and genetic data related to PAM, particularly myofibrillar myopathies, physicians should be careful when diagnosing patients with sporadic PAM.

Pendulichytrium sphaericum gen. et sp. nov. (Chytridiales, Chytriomycetaceae), a new chytrid parasitic on the diatom, Aulacoseira granulata

During the last decade, our concept of chytrid systematics has dramatically changed based on molecular phylogeny and zoospore ultrastructure. In contrast with well-studied saprotrophic chytrids, only a few obligate parasitic chytrids have been investigated with modern methods. Here, we investigate the novel chytrid culture KS93 that is parasitic on the diatom Aulacoseira granulata. Thallus morphology of KS93 was characterized by a spherical, stalked zoosporangium with a single, apical inoperculate discharge pore and zoospore discharge as a mass in a vesicle. A cross-inoculation experiment revealed that the infection of KS93 was specific to A. granulata. Zoospores of KS93 possessed the characters of the Group I type zoospore of the Chytriomycetaceae in the Chytridiales, but does not appear to have a paracrystalline inclusion. Additionally, KS93 also possessed a globule-type KAS (kinetosome-associated structure), first reported here for members of Chytriomycetaceae. In our molecular phylogeny, KS93 was placed in the basal position of the Chytriomycetaceae and was distinguished from any known species in the family. Morphological features of KS93 were distinct from those of any other taxa in the Chytriomycetaceae and from any described chytrids. Based on these results, we describe this chytrid as Pendulichytrium sphaericum gen. et sp. nov. in the family Chytriomycetaceae.

Transcriptome sequencing and delimitation of sympatric Oscarella species (O. carmela and O. pearsei sp. nov) from California, USA.

The homoscleromorph sponge Oscarella carmela, first described from central California, USA is shown to represent two superficially similar but both morphologically and phylogenetically distinct species that are co-distributed. We here describe a new species as Oscarella pearsei, sp. nov. and re-describe Oscarella carmela; the original description was based upon material from both species. Further, we correct the identification of published genomic/transcriptomic resources that were originally attributed to O. carmela, and present new Illumina-sequenced transcriptome assemblies for each of these species, and the mitochondrial genome sequence for O. pearsei sp. nov. Using SSU and LSU ribosomal DNA and the mitochondrial genome, we report the phylogenetic relationships of these species relative to other Oscarella species, and find strong support for the placement of O. pearsei sp. nov. in a distinct clade within genus Oscarella defined by the presence of spherulous cells that contain paracrystalline inclusions; O. carmela lacks this cell type. Oscarella pearsei sp. nov and O. carmela can be tentatively distinguished based upon gross morphological differences such as color, surface texture and extent of mucus production, but can be more reliably identified using mitochondrial and nuclear barcode sequencing, ultrastructural characteristics of cells in the mesohyl, and the morphology of the follicle epithelium which surrounds the developing embryo in reproductively active individuals.

Testicular, spermatogenesis and sperm morphology in Martarega bentoi (Heteroptera: Notonectidae)

The testicular, spermatogenesis and sperm morphology of the backswimmer Martarega bentoi was described using light and transmission electron microscopy. In this species, a pair of testes, two deferent ducts, two different pairs of accessory glands, and an ejaculatory duct form the male reproductive system. Each testis consists of two testicular follicles, which are arranged side by side in snail shape. The follicles are filled with cysts at different stages of spermatogenesis, but in the same cyst the germ cells (up to 64) are in the same stage. At the end of spermatogenesis, the sperm cells are very long, with the flagellum measuring approximately 2500 μm in length, the nucleus only 19 μm, and the acrosome, with two distinct regions, 300 μm. The flagellum is composed of an axoneme, with a 9 + 9 + 2 microtubular pattern, and 2 asymmetric mitochondrial derivatives (MDs). These have the anterior ends inserted into two cavities at the nucleus base, exhibit two paracrystalline inclusions, and have bridges linking them to the axoneme. Few spermatozoa per cyst, asymmetry in size and shape of the MDs, as well as their insertion at the nuclear base are characteristics considered derived, and that differentiate the sperm of M. bentoi from those of the Nepomorpha, Belostomatidae and Nepidae.

The Spectrum of Mitochondrial Ultrastructural Defects in Mitochondrial Myopathy.

Mitochondrial functions are intrinsically linked to their morphology and membrane ultrastructure. Characterizing abnormal mitochondrial structural features may thus provide insight into the underlying pathogenesis of inherited and acquired mitochondrial diseases. Following a systematic literature review on ultrastructural defects in mitochondrial myopathy, we investigated skeletal muscle biopsies from seven subjects with genetically defined mtDNA mutations. Mitochondrial ultrastructure and morphology were characterized using two complimentary approaches: transmission electron microscopy (TEM) and serial block face scanning EM (SBF-SEM) with 3D reconstruction. Six ultrastructural abnormalities were identified including i) paracrystalline inclusions, ii) linearization of cristae and abnormal angular features, iii) concentric layering of cristae membranes, iv) matrix compartmentalization, v) nanotunelling, and vi) donut-shaped mitochondria. In light of recent molecular advances in mitochondrial biology, these findings reveal novel aspects of mitochondrial ultrastructure and morphology in human tissues with implications for understanding the mechanisms linking mitochondrial dysfunction to disease.

Selected Case From the Arkadi M. Rywlin International Pathology Slide Series

A 43-year-old female patient diagnosed with chronic progressive external ophthalmoplegia (CPEO) because of mitochondrial myopathy documented by muscle biopsy is presented. The chief complaints were represented by blepharoptosis and ophthalmoplegia. The muscle biopsy was evaluated by histology, using the appropriate histochemical and histoenzimological stains. Ragged red fibers with Gomori trichrome stain were seen, which showed cytochrome c oxydase deficiency and abnormal succinate dehydrogenase staining in around 20% of muscle fibres. Electron microscopy was also performed which demonstrated abnormal, hyperplastic, pleomorphic, and hypertrophic mitochondria, characterized by paracrystalline inclusions arranged in parallel rows ("parking-lot" inclusions), consisting of rectangular arrays of mitochondrial membranes in a linear or grid-like pattern. In conclusion, mitochondrial myopathy was definitely diagnosed. Although molecular analysis, which was subsequently carried out, failed to reveal mutations in the mitochondrial DNA or in selected nuclear genes, the pathologic diagnosis was not changed. The differential diagnosis of CPEO with other forms of ocular myopathies as well as the possible association of CPEO with systemic syndromes is discussed. Ophtalmologists and medical internists should always suspect CPEO when dealing with patients affected by ocular myopathy, either in its pure form or in association with other myopathic or systemic signs.

G.P.190: Multiple deletions in mitochondrial DNA in myofibrillar myopathy and centronuclear myopathy

Multiple deletions in mitochondrial DNA (mtDNA) are associated with mutations in nuclear genes which encode proteins either directly or indirectly involved in the replication or maintenance of mtDNA. To date, mutations in twelve nuclear genes, POLG, POLG2, C10orf2, SLC25A4, RRM2B, TK2, MPV17, DGUOK, OPA1, MFN2, MGME1, and DNA2 have been identified in patients with multiple deletions in mtDNA, yet the genetic cause of multiple mtDNA deletions still remains undefined in a large number of patients. In addition to patients with a classic mitochondrial myopathy, multiple mtDNA deletions are also found in patients with myopathies such as sporadic IBM. Mitochondrial changes have also been identified in skeletal muscle from patients with myofibrillar myopathy, with histochemical changes such as rubbed out fibres observed with COX and NADH staining, and focal clustering and depletion of mitochondria. Mitochondrial pathology, including COX negative and ragged red fibres, and paracrystalline inclusions have also been described in patients with centronuclear myopathy due to mutations in DNM2, which encodes Dynamin 2, a GTPase which is involved in membrane trafficking. Here we describe our findings in two patients with multiple mtDNA deletions. In one patient, a 70 year old male who presented with a history of exercise induced muscle pain and distal myopathy we identified a novel pArg2364His mutation in the gene FLNC which encodes the actin binding protein filamin-C. In the second patient, a 40 year old male who presented at age 3 years with ataxia and later developed facial myopathy, proximal muscle weakness, and CPEO, histochemical investigation indicated centronuclear myopathy, and a p.Glu560Lys mutation in DNM2 was identified. Our findings suggest that FLNC and DNM2 should be added to the list of genes associated with multiple deletions in mtDNA.

Hirano bodies differentially modulate cell death induced by tau and the amyloid precursor protein intracellular domain.

BackgroundHirano bodies are actin-rich paracrystalline inclusions found in brains of patients with Alzheimer’s disease (AD), frontotemporal dementia (FTD), and in normal aged individuals. Although studies of post-mortem brain tissue provide clues of etiology, the physiological function of Hirano bodies remains unknown. A cell culture model was utilized to study the interactions of mutant tau proteins, model Hirano bodies, and GSK3β in human astrocytoma cells.ResultsMost tau variants showed co-localization with model Hirano bodies. Cosedimentation assays revealed this interaction may be direct, as recombinant purified forms of tau are all capable of binding F-actin. Model Hirano bodies had no effect or enhanced cell death induced by tau in the absence of amyloid precursor protein intracellular domain (AICD). In the presence of AICD and tau, synergistic cell death was observed in most cases, and model Hirano bodies decreased this synergistic cell death, except for forms of tau that caused significant cell death in the presence of Hirano bodies only. A role for the kinase GSK3β is suggested by the finding that a dominant negative form of GSK3β reduces this synergistic cell death. A subset of Hirano bodies in brain tissue of both Alzheimer’s disease and normal aged individuals was found to contain tau, with some Hirano bodies in Alzheimer’s disease brains containing hyperphosphorylated tau.ConclusionThe results demonstrate a complex interaction between tau and AICD involving activation of GSK3β in promoting cell death, and the ability of Hirano bodies to modulate this process.