Molecular genetics of mucopolysaccharidosis type IIIA and IIIB: Diagnostic,clinical, and biological implications

Mucopolysaccharidosis (MPS) types IIIA, B, C, and D are a group of autosomal recessive lysosomal storage diseases caused by mutations in one of four genes which encode enzyme activities required for the lysosomal degradation of heparan sulfate. The progressive lysosomal storage of heparan sulfate eventually results in the clinical onset of disease, which is predominantly characterized by severe central nervous system degeneration. MPS‐IIIA and MPS‐IIIB involve deficiencies of heparan sulfate sulfamidase (SGSH) and α‐N‐acetylglucosaminidase (NAGLU), respectively. Both the SGSH and NAGLU genes have been cloned and characterized, thereby permitting mutation analysis of MPS‐IIIA and MPS‐IIIB patients. A total of 62 mutations have now been defined for MPS‐IIIA consisting of 46 missense/nonsense mutations, 15 small insertions/deletions, and one splice site mutation. A total of 86 mutations have been identified in the NAGLU gene of MPS‐IIIB patients; 58 missense/nonsense mutations, 27 insertions/deletions, and one splice site mutation. Most of the identified mutations in the SGSH and NAGLU genes are associated with severe clinical phenotypes. Many of the missense, nonsense, and insertion/deletion mutations have been expressed in mammalian cell lines to permit the characterization of their effects on SGSH and NAGLU activity and intracellular processing and trafficking. For MPS‐IIIA and MPS‐IIIB many of the reported mutations are unique making screening the general population difficult. However, molecular characterization of MPS‐IIIA patients has revealed a high incidence of particular mutations of different geographical origins, which will be beneficial for the molecular diagnosis of MPS‐IIIA. Hum Mutat 18:264–281, 2001. © 2001 Wiley‐Liss, Inc.     

Longitudinal brain volumetric changes during one year in non-elderly healthy adults: a voxel-based morphometry study

Previous cross-sectional magnetic resonance imaging (MRI) studies of healthy aging in young adults have indicated the presence of significant inverse correlations between age and gray matter volumes, although not homogeneously across all brain regions. However, such cross-sectional studies have important limitations and there is a scarcity of detailed longitudinal MRI studies with repeated measures obtained in the same individuals in order to investigate regional gray matter changes during short periods of time in non-elderly healthy adults. In the present study, 52 healthy young adults aged 18 to 50 years (27 males and 25 females) were followed with repeated MRI acquisitions over approximately 15 months. Gray matter volumes were compared between the two times using voxel-based morphometry, with the prediction that volume changes would be detectable in the frontal lobe, temporal neocortex and hippocampus. Voxel-wise analyses showed significant (P < 0.05, family-wise error corrected) relative volume reductions of gray matter in two small foci located in the right orbitofrontal cortex and left hippocampus. Separate comparisons for males and females showed bilateral gray matter relative reductions in the orbitofrontal cortex over time only in males. We conclude that, in non-elderly healthy adults, subtle gray matter volume alterations are detectable after short periods of time. This underscores the dynamic nature of gray matter changes in the brain during adult life, with regional volume reductions being detectable in brain regions that are relevant to cognitive and emotional processes.     

Longitudinal mapping of mouse cerebral blood volume with MRI

MRI estimations of cerebral blood volume (CBV), useful in mapping brain dysfunction, typically require intravenous (IV) injections of contrast agents. Transgenically engineered mice have emerged as the dominant animal model with which to investigate disorders of the brain and novel therapeutic agents. The difficulty in gaining IV access in mice prohibits repeated administration of contrast in the same animal, limiting the ability to map CBV changes over time. Here we address this limitation by first optimizing an approach for estimating CBV that relies on intraperitoneal (IP) rather than IV injections of the contrast agent gadodiamide. Next, we show that CBV maps generated with IP or IV injections are quantitatively comparable. Finally, we show that CBV maps generated with IP gadodiamide can be acquired repeatedly, reliably and safely over time. Although this approach has certain limitations, estimating CBV with IP injections is well-suited for mapping the spatiotemporal pattern of brain dysfunction in mice models of disease, and for testing pharmacological agents.     

Retrovirally transduced bone marrow has a therapeutic effect on brain in the mouse model of mucopolysaccharidosis IIIB

Mucopolysaccharidosis IIIB (MPS IIIB) is a lysosomal storage disorder caused by mutations in NAGLU, the gene encoding alpha-N-acetylglucosaminidase. The disease is characterized by profound mental retardation and eventual neurodegeneration, but relatively mild somatic manifestations. There is no available therapy. We have used a mouse knockout model of the disease to test therapy by genetically modified bone marrow. Bone marrow from Naglu -/- male mice was transduced with human NAGLU cDNA in an MND-MFG vector, and transplanted into 6- to 8-week-old lethally irradiated female -/- mice. Sham-treated mice received bone marrow transduced with eGFP cDNA in an MND vector. alpha-N-Acetylglucosaminidase activity in plasma and leukocytes, measured 3 and 6 months after transplantation, varied from marginal to nearly 30 times wild-type. A low level of alpha-N-acetylglucosaminidase activity, as little as provided by transplantation of unmodified Naglu +/+ bone marrow, could normalize biochemical defects (glycosaminoglycan storage and beta-hexosaminidase elevation) in liver and spleen, but a very high level was required for an effect on kidney. Effects on the brain were best seen by examination of cellular morphology using light and electron microcopy. Mice that expressed very high levels of alpha-N-acetylglucosaminidase in blood had an increased number of normal-appearing neurons in the cortex and other parts of the brain, while microglia with engorged lysosomes had almost completely disappeared. Immunohistochemistry showed a marked decrease of staining for subunit c of mitochondrial ATP synthase and for Lamp1, markers of neuronal and microglial pathology, respectively, as well as a decrease in staining for glial fibrillary acid protein, a marker of activated astrocytes. These results show that genetically modified cells of hematopoietic origin can reduce the pathologic manifestations of MPS IIIB in the Naglu -/- mouse brain.     

I. Longitudinal changes in aging brain function

Changes in brain activity over time were evaluated in a group of older adults in the Baltimore Longitudinal Study of Aging who maintained good physical and cognitive health. Participants underwent PET scans during rest and delayed verbal and figural recognition memory performance at year 1 baseline and at year 9. While memory performance remained stable over the 8 years, longitudinal changes in regional cerebral blood flow were observed within each scan condition. Further analyses revealed distinctive patterns of change related specifically to verbal or figural recognition, as well as longitudinal changes common to all scan conditions. These findings demonstrate that the older brain undergoes functional reorganization with increasing age in healthy, cognitively stable individuals. In view of the stable memory performance, the task-dependent results suggest that age-related changes in brain activity help maintain cognitive function with advancing age.     

Accelerated clinical disease and pathology in mucopolysaccharidosis type IIIB and GalNAc transferase double knockout mice

Mucopolysaccharidosis type IIIB (MPS IIIB) is a neuropathic lysosomal storage disorder (LSD) resulting from an inherited deficiency of N-acetyl-α-d-glucosaminidase (Naglu) activity, an enzyme required to degrade the glycosaminoglycan heparan sulfate (HS). A deficiency in Naglu activity leads to lysosomal accumulation of HS as a primary storage substrate, and the gangliosides GM2 and GM3 as secondary accumulation products. To test the effect on neuropathogenesis of ganglioside accumulation, we bred mice deficient in both Naglu and GalNaAcT activities. The latter is the enzyme required for synthesis of GM2 and other complex gangliosides. Contrary to our expectation and to double knockout (DKO) studies where GalNAcT was knocked out in combination with other LSDs, our DKO mice showed a drastically shortened lifespan (24.5±1.4weeks, versus 50.5±0.9weeks (MPS IIIB), and 38.6±1.2weeks (GalNAcT)). To confirm that HS storage was the primary element resulting in the accelerated disease in our DKO mice, and not a locus tightly linked to the Naglu gene, we replicated our study with MPS IIIA mice, and found a virtually identical result (27.5±1.8weeks, versus 53.8±1.6weeks). All DKO mice showed motor signs of hind limb ataxia and hyper-extension, which were not seen in single KO or normal mice. At approximately 5months of age, the MPS IIIB-DKO showed a unique pattern of vacuolization and nerve fiber degeneration in the corpus callosum, seen only in the DKO mice, as well as the relatively early intracytoplasmic vacuolation of many neurons and glia characteristic of the MPS IIIB mice. We analyzed motor performance on a rocking Rota-Rod beginning at 3months of age. The MPS IIIA-DKO and MPS IIIB-DKO mice showed impaired performance and were statistically different from all parental lines. In particular, the MPS IIIB-DKO mice were significantly different from the parent MPS IIIB strains at 3, 5, and 6months (p≤0.0245). In conclusion we identified an accelerated phenotype associated with MPS IIIB within a DKO model system which showed white matter changes, with attendant performance deficits and a drastically shortened lifespan. This was in stark contrast to our expectations of a salutary response to the elimination of GM2. Despite this, the accelerated pathology and clinical signs represent a potentially improved system to study MPS IIIB neuropathogenesis as well as the role of complex gangliosides in normal CNS function.     

Listeria monocytogenes subgroups IIIA, IIIB, and IIIC delineate genetically distinct populations with varied pathogenic potential

Listeria monocytogenes lineage III strains belonging to subgroups IIIA (n = 8), IIIB (n = 5), and IIIC (n = 6) were examined along with other known serotype strains (n = 11) by PCR and Southern hybridization using several recently described species-, virulence-, and serotype-specific primers and probes. The virulence of seven representative lineage III strains was then evaluated in mice via the intraperitoneal route. The results suggest that subgroup IIIA consists of typical rhamnose-positive avirulent serotype 4a and virulent serotype 4c strains, subgroup IIIC consists of atypical rhamnose-negative virulent serotype 4c strains, and subgroup IIIB consists of atypical rhamnose-negative virulent non-serotype 4a and non-serotype 4c strains, some of which may be related to serotype 7. It is possible that subgroup IIIB (including serotype 7) may represent a novel subspecies within L. monocytogenes.     

Innervation of the humerus metaepiphysis in newborn and one year old children

Analysis of home and foreign literature on metaepiphyseal cartilage innervation and blood supply was presented, data on these organ diseases substantiate theoretical and clinical significance of the study was performed. Using macro-microscopic preparation, histological study, automatic image analyzer branches of humerus proximal metaepiphysis were shown to originate from axillary and subscapulary nerves. Nerves and vessels penetrating in the cartilaginous canals form neurovascular complexes. Cartilaginous canals are located unevenly. Nervous structures were found in the canals and their characteristics was given.     

Intellectual characteristics of diabetic children at diagnosis and one year later

Examined neurocognitive functions in 63 newly diagnosed pediatric patients with insulin-dependent diabetes mellitus (DM) at onset of illness (T0) and 1 year postdiagnosis (T1). Siblings (S) serving as controls were assessed at T0 only. Subjects were given age-appropriate tests of verbal and visuospatial abilities. In addition, DM were interviewed regularly during diabetes clinic to determine current diabetic control and different intervening glycemic-related events. Results revealed no differences between DM and S at T0, nor any specific impairment in DM predating illness. Also, DM did not demonstrate any acquired impairment after 1 year of illness. Children with early onset DM (less than 5 years) scored lower in spatial ability at T0 and T1 than children with later onset DM, who scored lower in verbal ability. Episodes of asymptomatic and mild chronic hypoglycemia correlated positively, not negatively, with improved outcome over time. There were no adverse effects of severe hypoglycemia. Ketonuria and hospitalizations were associated with lower performance IQs 1 year after onset, as was diabetic ketoacidosis at onset. Results are discussed in terms of critical periods of sensitivity of different brain regions to the effects of diabetes and the need for longer follow-up of these children.     

Cognitive and behaviour profiles of children with mucopolysaccharidosis Type II

Mucopolysaccharidosis Type II (MPS II) or Hunter Syndrome is a rare X-linked condition, due to a defect in a lysosomal enzyme involved in the breakdown of glycosaminoglycans. It is a progressive condition with worsening over time; however, symptom severity and progression rates vary. Normal intellectual function has been reported in males with mild MPS II but few studies are available that provide comprehensive cognitive profiles. Enzyme replacement therapy (ERT) can stabilize physical symptoms and has become standard treatment. Whether ERT can influence cognition is currently unknown. Considering this, we conducted cognitive, fine motor, and behavioural assessments with three males (7;6–12;1 years) with mild MPS II before and after ERT. Generally, cognition, fine motor skills, and behaviour were in the normal range; however, specific deficits in attention and executive function were identified. Following ERT, some memory improvements were seen. Executive deficits remained, and processing speed declined over time.     

Spinal cord compression in young children with type VI mucopolysaccharidosis

Spinal cord compression (SCC) is a known complication of mucopolysaccharidosis type VI (MPS VI) secondary to atlantoaxial subluxation, craniovertebral stenosis, posterior longitudinal ligament hypertrophy, or dural thickening. SCC is expected to occur in the natural history of the disease, regardless of enzyme replacement therapy (ERT), as intravenous enzyme does not cross the blood–brain barrier. We describe six MPS VI children with SCC, all diagnosed before 7 years of age. Within this group, four of the children were diagnosed with SCC after the introduction of ERT. We hypothesize that these patients may illustrate the previously undetected risk of increased joint mobility caused by ERT which may have contributed to increased cervical instability by loosening the neck joint, thus leading to or unmasking SCC. We reinforce the need for close follow-up of SCC, periodic neurological assessment, spine imaging, and neurophysiology in all MPS VI patients before and during ERT. Neurophysiological abnormalities may precede changes in MRI images (as shown in patients 4 and 5 from this sample) and should, therefore, be accessed in MPS VI patient evaluations, allowing for timely intervention and better prognosis. We recognize the limitations of these data due to the small sample size and recommend further investigation into this patient population.     

未服药的强迫障碍患者脑灰质体积异常的MRI研究

目的:应用脑磁共振成像(MRI)基于体素的形态测量学(VBM)比较未服药的强迫障碍患者脑灰质体积与正常人群间的差异,并探讨强迫障碍患者脑灰质体积的改变与临床现象之间的相关性。方法:纳入符合美国精神障碍诊断与统计手册第4版(DSM-Ⅳ)诊断标准的20例未服药的强迫障碍门诊患者,以及20名性别、年龄和受教育程度相匹配的健康对照。所有被试均接受头部磁共振扫描。采用VBM的分析方法,比较强迫障碍患者与健康对照之间脑灰质体积的差异。采用耶鲁-布郎强迫量表(Y-BOCS)、汉密顿抑郁量表(HAM D)、汉密顿焦虑量表(HAM A)评估临床症状。在控制焦虑、抑郁症状的前提下,分析强迫障碍患者异常的脑灰质体积与临床现象之间的关系。结果:与对照组相比,强迫障碍组的眶额回、颞上回、颞下回、小脑、楔前叶、辅助运动区及中央后回的灰质体积减少(P0.05,Al-phaSim校正);眶额回灰质体积的减少与Y-BOCS量表总分呈负相关(r=-0.49,P0.05)。结论:本研究结果提示眶额-纹状体-丘脑环路中的眶额回在强迫障碍的发生中起重要的作用,其他脑区如颞叶和小脑灰质体积减少,可能也参与了强迫障碍的发生。     

Modeling dynamic cerebral blood volume changes during brain activation on the basis of the blood-nulled functional MRI signal

Recently, vascular space occupancy (VASO) based functional magnetic resonance imaging (fMRI) was proposed to detect dynamic cerebral blood volume (CBV) changes using the blood-nulled non-selective inversion recovery (NSIR) sequence. However, directly mapping the dynamic CBV change by the NSIR signal change is based on the assumption of slow water exchange (SWE) around the capillary regime without cerebral blood flow (CBF) effects. In the present study, a fast water exchange (FWE) model incorporating with flow effects was derived from the Bloch equations and implemented for the quantification of dynamic CBV changes using VASO-fMRI during brain activation. Simulated results showed that only subtle differences in CBV changes estimated by these two models were observed on the basis of previously published VASO results. The influence of related physiological and biophysical factors within typical ranges was evaluated in steady-state simulations. It was revealed that in the transient state the CBV curves could be delayed in comparison with measured NSIR curves owing to the imbalance between the inflowing and outflowing blood signals.     

A fast way to visualize the brain surface with volume rendering of MRI data

The preprocessing of 3-dimensional (3D) MRI data constitutes a bottleneck in the process of visualizing the brain surface with volume rendering. As a fast way to achieve this preprocessing, the authors propose a simple pipeline based on an algorithm of seed-growing type, for approximate segmentation of the intradural space in T1-weighted 3D MRI data. Except for the setting of a seed and four parameters, this pipeline proceeds in an unsupervised manner; no interactive intermediate step is involved. It was tested with 15 datasets from normal adults. The result was reproducible in that as long as the seed was located within the cerebral white matter, identical segmentation was achieved for each dataset. Although the pipeline ran with gross segmentation error along the floor of the cranial cavity, it performed well along the cranial vault so that subsequent volume rendering permitted the observation of the sulco-gyral pattern over cerebral convexities. Use of this pipeline followed by volume rendering is a handy approach to the visualization of the brain surface from 3D MRI data.     

Morphological brain changes associated with Schneider's first-rank symptoms in schizophrenia: a MRI study

BACKGROUND: Schneider's first-rank symptoms involve an alienated feature of the sense of one's own mental or physical activity. To clarify the brain morphological basis for the production of these symptoms, volumes of the frontal and medial temporal regions and their clinical correlates were examined in patients with schizophrenia. METHOD: Twenty-two patients with schizophrenia and 44 age- and gender-matched healthy control subjects were included. All patients were in their psychotic episodes with definite Schneiderian symptoms, rated by using the Scale for Assessment of Positive Symptoms. Volumetric measurements of high-resolution magnetic resonance imaging were performed in the prefrontal area, cingulate gyrus, and precentral gyrus, and the medial temporal structures such as the amygdala, hippocampus, and parahippocampal gyrus. RESULTS: Patients had significantly decreased volumes in the cingulate gray matter and the amygdala compared to controls. In the patient group, Schneiderian symptom severity showed significant inverse correlations with volumes of the right posterior cingulate gray matter and of the left anterior parahippocampal gyrus. CONCLUSIONS: Schneiderian symptoms may be associated with morphological abnormalities in the limbic-paralimbic regions such as the cingulate gyrus and parahippocampal gyrus, which possibly serve the self-monitoring function and the coherent storage and reactivation of information.     

特发性全面性癫痫患者大脑结构异常改变的MRI研究

目的 基于深度学习脑龄预测方法和FreeSurfer图像分析软件,探讨特发性全面性癫痫（IGE）患者大脑形态结构的异常改变。方法 回顾性病例对照研究。纳入2020年1月—2021年12月山东省立医院及寿光市人民医院神经内科确诊的144例IGE患者。其中男84例、女60例,年龄10~70岁。基于公共脑成像数据库（人类连接组项目、中国人类连接组项目）建立正常人脑T₁加权像（T₁WI）MRI训练深度学习脑龄预测模型,并输入脑皮质及脑白质脑图。将IGE患者T₁WI MRI输入脑龄预测模型,获取预测脑龄。将27例未经治疗的早期IGE患者设为观察组,男18例、女9例,年龄（16.1±3.2）岁;招募与观察组年龄、性别匹配的29名健康志愿者作为对照组,男19例、女10例,年龄（16.4±4.5）岁,均行MR检查。观察项目：（1）比较IGE患者不同年龄段（10~20岁、>20~30岁、>30~40岁、>40~50岁、>50~60岁、>60~70岁）大脑的预测年龄与实际年龄的差异。（2）利用FreeSurfer软件,分析和比较观察组与对照组大脑皮质体积、厚度和表面积,以及局部形态的差异。结果 （1）IGE患者的不同年龄段中,除>30~40岁外（t=-1.58,P=0.138）,脑龄预测值均大于实际年龄,差异均有统计学意义（P值均<0.05）。（2）观察组与对照组的年龄、性别、教育程度等基线资料差异均无统计学意义（P值均>0.05）。与对照组比较,观察组大脑左、右半球皮质厚度略变薄,差异有统计学意义（t=3.91、3.40,P值均<0.01）;2组大脑半球皮质体积、表面积无明显变化,差异均无统计学意义（P值均>0.05）。与对照组相比,观察组脑区中右侧眶额皮质体积增大,无脑区皮质体积减小;右侧中央后回、左侧中央沟附近中央后回、右侧舌回后部分、左侧舌回及楔叶的皮质厚度均增加,右侧中央前回、双侧额上回（背侧）、右侧内嗅皮质的皮质厚度均减小;右侧海马旁回的皮质表面积增大,无脑区的皮质表面积减小。观察组左、右侧苍白球及右侧丘脑体积较对照组缩小,差异均有统计学意义（t=4.01、4.23、2.12,P值均<0.05）。2组左侧丘脑及双侧尾状核、壳核、海马及杏仁核体积比较,差异均无统计学意义（P值均>0.05）。结论 IGE患者在多个年龄段其脑结构都会发生异常改变。早期IGE患者的大脑皮质及皮质下核团仅发生细微结构的异常改变。     

痉挛型偏瘫儿童手节区形态学变化的MRI研究

目的 探讨痉挛型偏瘫患儿手节区（HKR）形态学变化的MRI征象。方法 回顾性病例对照研究。纳入2016年3月—2019年7月西安交通大学第一附属医院儿科确诊并行头颅MR检查的痉挛型偏瘫患儿14例为病例组,其中男8例、女6例,年龄（3.9±2.1）岁;MRI主要表现为脑室周围白质软化11例,脑灰质损伤4例,其中1例白质灰质均有损伤。另纳入28例健康儿童作为对照组,其中男16例、女12例,年龄（4.1±2.0）岁,其年龄、性别构成和双侧半球HKR类型均与病例组相匹配。基于MR 3D-T₁WI数据,在HKR的最佳评估层面（以在T₁WI轴位影像上观察到双侧额上沟位于双侧半球前中部、中央沟深达同侧半球内1/3处,同时可良好观察到HKR形态的层面为最佳评估层面）测量及计算2组受试者两侧半球HKR皮层厚度、高度、基底宽度、白质高度、高度与皮层厚度之比和高度与基底宽度之比等形态学指标。采用配对t检验、独立样本t检验或秩和检验,对各指标观察结果进行组内、组间统计学分析比较。采用组内相关系数检验观察者间、观察者内测量的一致性。结果 2组儿童年龄、性别和双侧HKR类型等基线资料比较,差异均无统计学意义（P值均>0.05）。病例组患儿受累侧HKR高度/皮层厚度（3.41±1.03）和HKR白质高度/皮层厚度（2.41±1.03）均小于未受累侧半球HKR（分别为3.96±1.17和2.96±1.17）,差异均有统计学意义（t=2.49、2.49,P值均<0.05）;其余各指标组内比较,差异无统计学意义（P值均>0.05）。病例组患儿受累侧半球HKR高度（7.13±1.40）mm、HKR白质高度（4.89±1.47）mm、HKR高度/皮层厚度（3.41±1.03）和HKR白质高度/皮层厚度（2.41±1.03）均小于对照组相对应一侧[（8.65±1.01） mm,（6.77±0.99） mm,4.70±0.79和3.70±0.79],差异有统计学意义（t=2.91、3.58、3.71、3.71,P值均<0.05）;其余各指标组间比较,差异无统计学意义（P值均>0.05）。结论 痉挛型偏瘫患儿受累侧半球HKR皮层厚度、基底宽度改变不明显,但白质高度减小。