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A Knowledge-Enhanced Multimodal Framework with Genomic Reconstruction for DLBCL Drug Response Prediction.

Diffuse large B-cell lymphoma (DLBCL) exhibits substantial biological heterogeneity, leading to pronounced variability in patient response to therapy. Accurate drug response prediction is therefore critical for precision treatment but remains challenging in clinical settings where genomic sequencing, a highly informative modality, is frequently incomplete. Existing methods, often developed from cell-line pharmacogenomic datasets or single-modality data, typically assume fully observed molecular profiles and thus show limited robustness under missing genomic data. To address this limitation, a knowledge-enhanced multimodal framework with genomic reconstruction (KeM-DRP) is proposed for individualized drug response prediction in DLBCL. The framework models the central role of genomics by integrating biological prior knowledge through a gene-pathway-biological process hierarchy, enabling robust representation learning from sparse observations. To compensate for missing genomic measurements, a cross-modal genomic compensation module reconstructs genomically informed latent features from routinely available clinical modalities. Furthermore, a genomics-guided adaptive fusion strategy dynamically integrates heterogeneous modalities conditioned on observed or reconstructed genomic representation. Experiments on a real-world DLBCL cohort demonstrate that KeM-DRP consistently outperforms competitive baselines. The reconstructed genomic representation represents most predictive utility, highlighting the robustness and practical value of the framework under incomplete genomic data.

Journal Article↗

Responses of single spinal motoneurons to magnetic brain stimulation in healthy subjects and patients with multiple sclerosis.

Magnetic stimuli delivered over the scalp can cause single motor units to discharge in intrinsic hand muscles. The discharge characteristics of 26 tonically active, low threshold single motor units in the first dorsal interosseous muscle of 13 healthy subjects and of 21 motor units in 9 patients with multiple sclerosis (MS) were studied. Up to 500 transcranial magnetic stimuli were delivered at the vertex and were given randomly with respect to, or at a fixed delay after, the previous voluntary discharge. Peristimulus time histograms (PSTHs) of motor unit discharges were constructed. In healthy subjects, two periods of increased firing probability were seen at onset latencies of 20-31 ms and 56-90 ms after the stimulus. These periods have been termed the primary peak and the secondary peak. The primary peak had a mean duration of 4.6 ms and was found to be multimodal in 17 motor units. Subpeaks had intermodal intervals of between 0.6 and 2.4 ms. Subpeaks probably result from a sequence of excitatory postsynaptic potentials (EPSPs) induced at the motoneuron by corticospinal impulses. In patients with MS, the primary peak could be absent, delayed in onset, of increased duration without discernible subpeaks, or showing increased intermodal intervals between subpeaks. In 3 motor units from patients with MS, PSTHs with normal features were found. It is postulated from this study of the corticospinal inputs to single motoneurons that motor impairment in MS can be due to a number of mechanisms including slowed conduction in corticospinal fibres, dispersion of arrival times of corticospinal impulses at spinal motoneurons and conduction block in corticospinal fibres, which may be frequency dependent.

Adult↗

EWS::WT1 Isoform-Dependent Regulation of Neogenes in Desmoplastic Small Round Cell Tumors.

Desmoplastic small round cell tumor (DSRCT) is a rare, aggressive sarcoma characterized by the pathognomonic EWS::WT1 fusion protein (FP), an oncogenic chimeric transcription factor (OCTF) resulting from the t(11;22)(p13;q12) translocation. Recent studies have identified "neogenes" (NGs), genes normally silent in normal tissues but transcriptionally activated by OCTFs, as potential tumor-specific markers in fusion-driven cancers. In this study, we investigated the expression and regulation of DSRCT-specific NGs (DSRCT_NGs) using multimodal data across different cohorts of patients, PDX, and cell line data. We evaluated bulk and single-nucleus RNA sequencing of patient specimens from MD Anderson Cancer Center, revealing the robust ability for DSRCT_NGs to distinguish FP-positive DSRCT from samples failing detection of the EWS::WT1 FP. To elucidate the regulatory role of the EWS::WT1 FP in driving NG expression, we performed knockdown experiments in four DSRCT cell lines. This consistently resulted in a reduction of DSRCT_NG expression. Isoform-specific expression of EWS::WT1 in LP9 and MeT-5A mesothelial cells revealed that the E-KTS isoform of EWS::WT1 predominantly drives DSRCT_NG expression. Mechanistically, ATAC-seq and ChIP-seq analyses demonstrated that EWS::WT1 directly binds to accessible chromatin regions near NG transcription start sites, enriched for WT1 motifs and active histone marks. Integration of Hi-ChIP data further revealed that EWS::WT1 facilitates long-range enhancer-promoter looping at DSRCT_NG loci, promoting the expression of nearby genes. Collectively, these findings establish DSRCT_NGs as direct transcriptional outputs of the EWS::WT1 FP and implicate their loci as regulatory regions of the DSRCT transcriptome. Their fusion-dependent expression, chromatin accessibility, and promoter-enhancer connectivity underscore their potential utility as highly specific biomarkers and therapeutic targets in DSRCT.

DSRCT↗

[Diagnostics and treatment strategies for soft tissue sarcomas].

Soft tissue sarcomas (STS) represent a rare entity of all malignant tumors (1%). Thus, an in-depth understanding of multidisciplinary treatment strategies may not be sufficiently present at all operative units. Consecutively, optimal diagnostic and therapeutical pathways may not be applied. Magnetic resonance imaging (MRI) is the procedure of choice in diagnosing STS. Biopsies should be performed in specialized centers. Identification of cytogenetic factors has become more important for the typing and prognosis of STS. Management of STS should employ multimodal treatment concepts (Oncology, Radiotherapy, Surgical Oncology). The decision on whether radiotherapy, chemotherapy or another option is indicated should be taken by an interdisciplinary tumor board, which also determines the sequence of treatment in relation to resection. To obtain sufficient information from histopathologic examination of the resected tumor, a clear and distinct definition of critical margins and topography by the surgeon is essential. Following these concepts, optimal local tumor control associated with resections preserving function and limbs is achieved without impairment of overall prognosis. Tumor resection alone, without previous evaluation and where appropriate adopting multimodal treatment strategies, no longer meets modern standards. After primary treatment is complete, patients have to be enrolled in a standardized follow-up program.

Biopsy↗

Multimodality imaging of tumor integrin alphavbeta3 expression.

Most solid tumors are angiogenesis dependent. Anti-angiogenic pharmaceuticals that inhibit the growth of new blood vessels offer considerable promise as anti-cancer agents. With increasing numbers of anti-angiogenic drugs in clinical trials, there is an urgent need for detailed characterization of the heterogeneity of tumor vasculature and dissection of the complex network of mechanisms that control tumor angiogenesis. Non-invasive molecular imaging will play a key role in individualized anti-angiogenic therapy based upon molecular features of the new blood vessel growth. Integrin alpha(v)beta(3), which binds several ligands via an RGD tripeptide sequence, is uniquely expressed in tumor vasculature and aggressive tumor cells, making it a potential target for anti-angiogenic interventions. This review highlights some recent advances in multimodality imaging of tumor integrin expression with emphasis on positron emission tomography (PET).

Drug Design↗

Surgical imaging systems.

Imaging i.n.surgery. is used for diagnosis, planning, intraoperative navigation and post-operative evaluation, DIgItal medical imaging modalities mclude computed tomography (CT), magnetic resonance Imaging (MRI), MR therapy (MRT), fluoroscopy and ultrasound.t These modalities are applied singly or jointly (multimodality) Surgical requirements differ according to the nature of intervention, and real-time guidance? is sometimes needed such that a sequence of images is generated and displayed as acquired, Soft copy display on CRTscreens is satisfactory for intraoperative use, while hardcopy film images or physical replica modeling may be needed in other cases. Computed tomography/ developed more than 20 years ago, remains important in craniofacial'v" and orthopedic surgery." Newer imaging systems, especially ultrasound, magnetic resonance imaging,'6 and digital fluoroscopy are used for neurosurgery, oncology, cardiothoracic and abdominal surgery. Each modality offers specific qualities that subserve specific needs in diagnosis, planning, intraoperative navigation and evaluation (Table 1).

Journal Article↗

Evaluation of a new treatment strategy for Paget-Schroetter syndrome: spontaneous thrombosis of the axillary-subclavian vein.

PURPOSE: The purpose of this study was to evaluate the efficacy of a staged, multimodal algorithm of therapy for durable correction of Paget-Schroetter syndrome. METHODS: Fifty consecutive patients were entered into a sequential treatment program for spontaneous axillary-subclavian vein thrombosis. Forty-three had initial thrombolytic or anticoagulant treatment followed by longer-term warfarin sodium therapy. Thirty-six (72%) underwent surgical correction of the underlying structural abnormality, and nine patients had postoperative balloon angioplasty. RESULTS: At the time of final evaluation, 93% of patients with a patent vein and 64% of those with an occluded vein were essentially free of symptoms. After surgical correction there were no episodes of recurrent thrombosis in a mean follow-up period of 3.1 years. Urokinase was the most effective pharmacologic agent for clot lysis (p = 0.003), and restoration of initial patency was the most significant factor in establishing final venous patency determined venographically (p = 0.0003). CONCLUSIONS: It was concluded that a staged, multimodal approach to the Paget-Schroetter syndrome can effectively restore venous patency, reduce rethrombosis, and return normal function. The most effective sequence included transcatheter thrombolytic therapy, 3 months of anticoagulation therapy with warfarin sodium, and transaxillary first rib resection and decompression, followed by balloon angioplasty in cases of residual stricture.

Adolescent↗

Towards natural stimulation in fMRI--issues of data analysis.

In search for suitable tools to study brain activation in natural environments, where the stimuli are multimodal, poorly predictable and irregularly varying, we collected functional magnetic resonance imaging data from 6 subjects during a continuous 8-min stimulus sequence that comprised auditory (speech or tone pips), visual (video clips dominated by faces, hands, or buildings), and tactile finger stimuli in blocks of 6-33 s. Results obtained by independent component analysis (ICA) and general-linear-model-based analysis (GLM) were compared. ICA separated in the superior temporal gyrus one independent component (IC) that reacted to all auditory stimuli and in the superior temporal sulcus another IC responding only to speech. Several distinct and rather symmetric vision-sensitive ICs were found in the posterior brain. An IC in the V5/MT region reacted to videos depicting faces or hands, whereas ICs in the V1/V2 region reacted to all video clips, including buildings. The corresponding GLM-derived activations in the auditory and early visual cortices comprised sub-areas of the ICA-revealed activations. ICA separated a prominent IC in the primary somatosensory cortex whereas the GLM-based analysis failed to show any touch-related activation. "Intrinsic" components, unrelated to the stimuli but spatially consistent across subjects, were discerned as well. The individual time courses were highly consistent in sensory projection cortices and more variable elsewhere. The ability to differentiate functionally meaningful composites of activated brain areas and to straightforwardly reveal their temporal dynamics renders ICA a sensitive tool to study brain responses to complex natural stimuli.

Acoustic Stimulation↗

Baseline magnetic resonance imaging parameters and stroke outcome in patients treated by intravenous tissue plasminogen activator.

BACKGROUND AND PURPOSE: We designed a prospective sequential pretreatment and posttreatment MRI study to assess the relation between neuroimaging parameters and clinical outcome in patients treated with intravenous recombinant tissue-type plasminogen activator (rtPA). METHODS: Patients with symptoms of acute hemispheric ischemic stroke were recruited. The National Institutes of Health Stroke Scale (NIHSS) score was assessed at baseline and at days 1, 7, and 60, and the modified Rankin scale (mRS) at day 60, by which outcome was classified in terms of independence (mRS score 0, 1, or 2) or severe disability or death (mRS score 3 through 6), was assigned. Multimodal stroke MRI was performed at presentation and repeated at day 1. MRI procedures included magnetic resonance angiography, T2* gradient-echo sequence, echoplanar imaging, and isotropic diffusion- (DWI) and perfusion-weighted (PWI) imaging. Patients were treated with intravenous rtPA after MRI completion. RESULTS: Twenty-nine patients (16 men and 13 women; mean+/-SD age, 65+/-14 years) underwent MRI; the mean time from symptom onset to treatment was 255+/-62 minutes. Twenty-six patients had a vessel occlusion, and 15 patients experienced a partial (Thrombolysis in Myocardial Infarction [TIMI]-2) or total (TIMI-3) recanalization at day 1, whereas 11 patients had a persistent occlusion. Mean NIHSS scores at day 60 were 5.7+/-5.4 if recanalization had occurred and 14+/-2 in cases of persistent occlusion. According to the mRS, 13 patients were independent (mRS 0 through 2), whereas severe disability or death (mRS 3 through 6) was observed in 15 patients. A better outcome was observed when recanalization was achieved (r=-0.68, P=0.0002). PWI volume and time to peak (TTP) within the DWI lesion assessed before therapy were correlated with day-60 NIHSS score (PWI volume: r=0.51, P=0.006, TTP: r=0.35, P=0.07). The day-0 DWI abnormality volume was well correlated with day-60 NIHSS score (r=0.58, P=0.001). Multiple regression linear analysis showed that 2 factors mainly influenced clinical outcome: (1) recanalization, with a high correlation with NIHSS score at day 60 (P=0.0001) and (2) day-0 DWI lesion volume, which is closely associated with day-60 NIHSS score (P=0.03). CONCLUSIONS: Baseline DWI volume and recanalization are the main factors influencing clinical outcome after rtPA for ischemic stroke.

Acute Disease↗

Multimodal anatomic, functional, and metabolic brain imaging for tumor resection.

OBJECTIVE: Improvement of neurosurgical techniques with a more detailed description of brain tumors and their functional environment. METHODS: We performed: (1) anatomical magnetic resonance imaging (MRI) for reference, (2) functional sequences dedicated to the adjacent cortical structures (sensorimotor, visual, language paradigms), and (3) thallium 201 cerebral tomoscintigraphy to visualize active tumor invasion. Data were transferred to a workstation for automatic registration. RESULTS: All data were combined into one synthetic image showing the foci of high proliferative activity, which have to be completely resected, and the peritumoral functional structures, which have to be spared in order to minimize postoperative sequelae. This trimodal image is entered into a surgical neuronavigation computer for preoperative planning in order to outline tumoral target and functional risk areas. All this information is displayed in the operative microscope (Zeiss MKM) optically linked to MR images. This multimodality technique diminishes operative time by reducing electrocorticography and improves the operative short-term outcome. CONCLUSION: Multimodal imaging is useful for optimization of neurosurgical tumor resection.

Adult↗

Mapping Protein Occupancy on DNA with an Unnatural Cytosine Modification.

The epigenome provides a dynamic layer of gene regulatory control above the static genetic sequence. DNA base modifications are key epigenetic regulators, predominantly found within CpG contexts in mammalian genomes. Working in tandem with these DNA modifications, chromatin-associated proteins and transcription factors further control gene expression. Given the interplay of these factors, concurrent mapping of DNA base modifications with protein-DNA occupancy can greatly aid in interpreting the epigenome. Existing multimodal mapping methods include the use of DNA methyltransferases to mark accessible, protein-unbound DNA in non-CpG contexts. However, such approaches can either confound readouts with native DNA modifications or constrain users to third-generation sequencing approaches. To circumvent these limitations, we explored the possibility of introducing an unnatural DNA base modification, 5-carboxymethylcytosine, as an alternative label for protein occupancy. Here, we report our efforts to rationally engineer non-CpG-specific DNA methyltransferases to take on neomorphic DNA carboxymethyltransferase (CxMTase) activities. We find that DNA carboxymethylation of cytosines in GpC contexts shows broad compatibility with the most widely used epigenetic detection methods and can be used to reliably report on protein occupancy states. Using this approach, we reveal the single-molecule binding patterns of LexA, a master repressor in the bacterial DNA damage (SOS) response, at its self-regulated and endogenously methylated promoter. We thus show that unnatural DNA modifications can uncover novel biological insights and potentiate new approaches to multimodal epigenetic profiling.

DNA↗

Convergence of multimodal sensory input onto higher-level neurons of the crayfish olfactory pathway.

Intracellular electrophysiological studies of lateral protocerebral interneurons (LPIs) in the crayfish Procambarus clarkii have revealed convergence of multimodal sensory information onto these higher-level cells of the crustacean central olfactory pathway. Antennular stimulation by odors or electrical shocks generates excitatory-inhibitory sequences in some LPIs as does electrical or hydrodynamic stimulation of the antennae. Photic stimulation of the ipsilateral compound eye generates excitatory responses in LPIs, usually in the form of trains of impulse bursts that are timed to the peaks of the spontaneous oscillatory activity that characterizes these neurons. Focal electrical stimulation of the olfactory lobe, the termination point of antennular afferent input, or the accessory lobe, where higher-level visual and tactile inputs converge, also generates brief excitation and a delayed, prolonged inhibition in LPIs. Both phases of this activity are thought to be transmitted to the lateral protocerebrum via deutocerebral projection neurons, which have extensive dendritic arborizations in the olfactory lobe and the accessory lobe. The excitatory pathway is thought to synapse directly with target LPIs, whereas the inhibitory pathway is probably indirect and mediated through GABAergic interneurons within the lateral protocerebrum. There is evidence that both presynaptic and postsynaptic inhibition suppress activity in LPIs. Preliminary observations suggest that a small cluster of neurons adjacent to the hemi-ellipsoid body are inhibitory to LPI activity. Multimodal inhibitory and excitatory modulation of LPI activity may play a part in the contextual identification of odors in the crayfish olfactory system.

Action Potentials↗

Implementation of T2*-weighted MR for multimodal image guidance in cerebral cavernomas.

The aim of this study was to evaluate the feasibility, the safety, and the usefulness of T2*-weighted magnetic resonance (MR) for neuronavigational guidance in patients with cerebral cavernomas. Eight patients with intracerebral cavernomas were operated assisted by T2*-weighted MR image-guidance. The cavernomas were either deep-seated or in eloquent regions. Image fusion of a contrast-enhanced T1-weighted gradient-echo (GRE) sequence with a T2*-weighted GRE sequence was performed via an automated fusion software (StealthMerge). The T2*-weighted images were used to secure complete resection of the cavernoma in all patients and to verify resection of surrounding hemosiderin-stained tissue in epilepsy cases. Furthermore, the multimodal neuronavigational concept included ultrasonography, corticography, and evoked potentials. Postoperative MR excluded any residual malformation in all cases. There was no postoperative morbidity; all epilepsy patients are seizure-free up to now. In our preliminary series, T2*-GRE-guided neuronavigation proved useful for resection control in cavernoma surgery, and we suppose that it will be helpful to clarify the discussion on the value of resection of the surrounding hemosiderin-stained tissue.

Adolescent↗

[Psychosocial factors in a fibromyalgia syndrome patient. Assessment by means of electron pain diaries--casuistics and multivariate time series analysis].

OBJECTIVE: Fibromyalgia syndrome (FMS) is a condition of chronic widespread pain. In its process of chronification psychosocial factors play an important role. A multimodal treatment including integrated group therapy has been proved to be effective. Yet little attention has been paid so far to the exact sequence of changes and interrelation between psychosocial factors, functional capacity, and level of pain under integrated group therapy for FMS patients. METHODS: One FMS patient was exemplarily monitored with an electronic diary over 13 weeks while undergoing integrated group therapy. On a daily basis we assessed the level of pain, functional capacity, and other disease-related variables (anxiety, depression, quality of sleep, self-efficacy) via visual analog scales. By the means of multivariate time series analysis the timing of changes in psychosocial factors and their effects on perceived functional capacity was identified. RESULTS: Under integrated group therapy all assessed variables gradually changed in the predicted way. Pain, depression, anxiety could be reduced, whereas self-efficacy, quality of sleep, and functional capacity improved. 71% of the variance could be explained by the multiple regression model. Self-efficacy was, beside pain intensity and depression, an important predictor for functional capacity on the same day. High self-efficacy correlated negatively with the level of functional capacity 3 days later. CONCLUSION: Integrated group therapy proved to be effective. Self-efficacy played an important role regarding the improvement of functional capacity. Depicting the exact timing of changes in the assessed variables helped to detect patterns of influence and indicate directions for further treatment.

Electronics↗

Pulmonary embolism: comparison of angiography with spiral computed tomography, magnetic resonance angiography, and real-time magnetic resonance imaging.

In the last decade, spiral computed tomography (CT) and magnetic resonance (MR) angiography (MRA) have become a viable alternative to conventional angiography in the diagnosis of acute pulmonary embolism. However, patients with dyspnea are often unable to hold their breath for a longer time and thus image degradation is frequently observed. Consequently, an imaging sequence that allows free breathing is desirable. The aim of this animal study was to compare contrast-enhanced spiral CT, MRA and a real-time MR sequence, the latter without breath-hold, with pulmonary angiography as reference gold standard. Nine pigs with artificially induced pulmonary embolism underwent this multimodality comparison. All images were independently evaluated for the presence of pulmonary emboli by two reviewers. Forty-three filling defects were detected by conventional angiography on lobar and segmental levels. Sensitivity of CT images was 72.1 and 69.8% for Readers 1 and 2, respectively, and sensitivity of MRA images was 79.1 and 81.4%. With real-time MR imaging, however, the detection rate was 97.7% for both readers. We conclude that, under experimental conditions, real-time MR imaging without the use of radiation or iodinated contrast material is comparable with angiography in the detection of pulmonary emboli.

Angiography, Digital Subtraction↗

Disruption of verbal STM by irrelevant speech, articulatory suppression, and manual tapping: do they have a common source?

Under appropriate conditions, immediate serial verbal recall is impaired by irrelevant speech, articulatory suppression, and syncopated tapping. Interpretation of these variables in terms of the phonological loop component of working memory assumes separate phonological storage and articulatory rehearsal processes. In contrast, the Object-Oriented Episodic Record (O-OER) of Jones and the feature theory of Neath interpret these and other phenomena in terms of a unitary multimodal system. Three experiments investigate these disrupting tasks, with each experiment emphasizing one parameter. In each case, recall of phonologically similar and dissimilar letter sequences is compared as a marker of the presence or absence of phonological coding. In Experiment 1, subjects heard or articulated a single item, or tapped a single key at equal intervals. Only articulatory suppression impaired performance; it also abolished the effects of phonological similarity. Experiment 2 was identical, except that items were heard, or generated in a syncopated rhythm. Both suppression and tapping impaired performance to an equivalent extent and obliterated the effect of phonological similarity. Syncopated irrelevant speech caused a modest but significant impairment in performance. Experiment 3 was identical to Experiment 1, except that six tokens were used. Irrelevant speech and tapping had a clear impact on recall, but neither removed the phonological similarity effect. Again articulatory suppression had a major impact on performance and removed the effect of phonological similarity. We conclude that the pattern of results readily fits the phonological loop hypothesis, provided one accepts Saitos proposal that generating syncopated sequences uses common processes with speech production. It is not clear how the results can be explained by either the O-OER or the feature hypothesis.

Acoustic Stimulation↗

Inflammatory breast carcinoma: outcomes with trimodality therapy for nonmetastatic disease.

BACKGROUND: The objectives of this study were to summarize a single-institution experience in treating patients with inflammatory breast carcinoma (IBC) using trimodality therapy and to identify prognostic factors for outcome. METHODS: Sixty-one women underwent radiation therapy with curative intent for IBC between 1982 and 2001. All but five women received trimodality therapy. Neoadjuvant chemotherapy was given to the majority of women (n = 43 patients), although some received "up-front" surgery as first therapy (n = 18 patients). RESULTS: With a median potential observation time after diagnosis of 14 years, freedom from locoregional disease progression was 78%, freedom from distant metastasis was 45%, and the cause-specific survival rate was 47% at 5 years. Approximately 40% of the 56 patients who received trimodality therapy remained free of disease. Multivariate analysis demonstrated three factors that were found to be associated significantly with improved cause-specific survival: pathologic tumor size < 4 cm (P = 0.0001), up-front surgery (P = 0.0078), and local disease control (P = 0.0003). Factors that were found to be associated with better freedom from locoregional disease progression were pathologic tumor size (< 4 cm; P = 0.0157), age (> 55 years; P = 0.0596), and radiation dose (> or = 60 grays [Gy]; P = 0.0621). CONCLUSIONS: IBC is an aggressive disease that is treated effectively in select patients by multimodality therapy. Patient outcomes may be improved with therapies that result in better local and systemic control. Further studies are warranted to address the optimal sequence of trimodality therapy and the optimal administration of each agent.

Adult↗

Telomeric repeats of Tetrahymena malaccensis mitochondrial DNA: a multimodal distribution that fluctuates erratically during growth.

The linear mitochondrial DNA (mtDNA) of Tetrahymena malaccensis has tandem 52-base-pair repeats at its telomeres. The mtDNA has a multimodal distribution of telomeres. Different groups in the distribution have different numbers of telomeric repeats. The standard deviation of the size of each end group is independent of the mean size of the end group. The two sides of the mtDNA have different multimodal distributions of repeats. Cloned cell lines have multimodal distributions of mtDNA telomeres distinct from that of the original cell line. The number of telomere end groups and the average size of the end groups change in an erratic fashion as the cells are passaged and do not reach a stable equilibrium distribution in 185 generations. We propose that the mean size of a telomere end group and the size distribution of an end group are independently regulated. The system controlling the average size of end groups may be defective in T. malaccensis, since a closely related species (T. thermophila) does not have a multimodal distribution of mtDNA telomeres. T. hyperangularis, which has different telomeric repeats on each side of its mtDNA, has a multimodal distribution of mtDNA telomeres on only one side, suggesting that the mechanism controlling the average number of repeats in an end group can be sequence specific. These mitochondrial telomeres provide a new example of the more general phenomenon of expansion and contraction of arrays of repeated sequences seen, for example, with simple-sequence "satellite" DNAs; however, the mitochondrial telomeres change on a very short time scale.

Animals↗