Spatial cognition in young children with spinal muscular atrophy

Success in visuospatial tasks has often been demonstrated in teenagers with spinal muscular atrophy (SMA). However, what has been tested in these studies, with the Wechsler Intelligence Scale for Children-Revised (Wechsler, 1974) performance scale, does not deal with the spatial capacities that co-occur with the advent of self-produced locomotion. Indeed, various studies have shown that occurrence of locomotion in infancy is correlated with the development of visuospatial cognitive competencies, suggesting that locomotor experience might play a central role in spatial development, especially in the realm of manual search for hidden objects. It is thus of interest to assess spatial search skills in SMA young children suffering total deprivation of locomotor experience. Twelve Type-2 SMA children with a mean age of 30 months were compared with controls with respect to their spatial search skills in a memory-for-locations task. In this search task, hiding containers were rotated 180° before search was permitted. The performance obtained with the SMA group did not differ from that obtained in the healthy control group. SMA patients searched correctly for a hidden object in the 3-choice search task. Locomotor impairment does not appear to be a key risk factor for dramatic slowing down or deviation in the development of spatial search skills, as assumed by some authors. Further research is needed to identify the alternative pathways to normal spatial development that are used by SMA young children.     

Theileriosis: cell-mediated and humoral immunity.

The protozoan parasite of cattle Theileria parva transforms lymphoid cells into permanently proliferating cell lines. Antibodies reacting with parasite antigens can be detected by several methods, but there is no evidence that they are protective. Two cellular responses to infection have been found. In immune animals powerful cytotoxicity restricted to syngeneic infected cells rapidly appears; this is thought to be mediated by T-lymphocytes and to play a major role in resistance to reinfection. In primary infections cytotoxicity against allogeneic infected and xenogeneic cells is observed late. This is thought to be due to activation of a nonspecific cytotoxic system, which contributes to the lymphocytolysis and panleukopenia, a prominent feature of the disease. If mounted early enough, the nonspecific effector mechanism could also contribute to recovery from a primary infection, when it occurs.     

15例儿童型脊肌萎缩症的基因分析

脊肌萎缩症(spinal muscular atrophy,SMA)是一种较常见的常染色体隐性遗传病,由于脊髓前角运动神经细胞退行性变,导致患者进行性骨骼肌无力和肌萎缩.根据发病年龄和病情轻重,临床上将SMA分为4型,Ⅰ、Ⅱ、Ⅲ型称为儿童型SMA,Ⅳ型为成人型SMA[1].小儿时期起病的SMA是要儿期最常见的致死性遗传病.     

Intact humoral and cell-mediated immunity in chronic marijuana smoking.

The immune system of 12 healthy chronic marijuana-smoking adults was evaluated while they smoked marijuana daily for 64 consecutive days under controlled hospitalized conditions. Studies included enumeration of B and T cell subpopulations, lymphocyte proliferative responses to PHA and to allogeneic cells, and serum immunoglobulin levels. Percent B cells, initially low in 2 patients, became normal. Baseline total B cells, determined either by surface immunoglobulins (338 cells/mm3 +/- 60 SEM) or complement receptors (162 cells/mms +/- 27) were significantly (p less than 0.05) less than control but increased to normal (485 +/- 97 and 239 +/- 47) over time. Percent T cells, initially low (less than 40%) in 4 patients, became normal. Baseline T cells (951 cells/mm3 +/- 70 SEM), significantly lower than controls (2,010 +/- 210, p less than 0.05), increased to normal by day 63 (1,875 +/- 281). In vitro lymphocyte response to graded doses of PHA and to allogeneic cells was normal initially and did not change over time. Serum IgG (1,064 +/- 33), IgA (166 +/- 13), and IgM (96 +/- 6) were normal. Serum IgE levels increased in 4 subjects without evidence of allergy. Short-term chronic marijuana use does not have a substantial adverse effect on B or T cells of young healthy adults.     

Animal models of spinal muscular atrophy

Proximal spinal muscular atrophy (SMA) is the second most common autosomal recessive inherited disorder in humans. It is the most common genetic cause of infant mortality. As yet, there is no cure for this neuromuscular disorder which affects the lower motor neurons and proximal muscles of the limbs and trunk. In the last decade, significant advances have been made in understanding this disease, from linkage analysis to isolating the defective gene and identifying its protein product. This review summarizes the most recent advance in SMA research: the development of animal models of the disease, in particular mouse models of SMA. The SMA mice that we describe here present with symptoms similar to those seen in SMA patients. They promise to further the understanding of the molecular basis of this disease and demonstrate the feasibility of using the intact SMN2 gene, found in all SMA patients, as a means of treating this disorder.     

Gene deletions in spinal muscular atrophy.

Two candidate genes (NAIP and SMN) have recently been reported for childhood onset spinal muscular atrophy (SMA). Although affected subjects show deletions of these genes, these deletions can lead to either a very mild or a severe phenotype. We have analysed a large number of clinically well defined patients, carriers, and normal controls to assess the frequency and extent of deletions encompassing both of these genes. A genotype analysis indicates that more extensive deletions are seen in the severe form of SMA than in the milder forms. In addition, 1 center dot 9% of phenotypically normal carriers are deleted for the NAIP gene; no carriers were deleted for the SMN gene. Our data suggest that deletions in both of these genes, using the currently available assays, are associated with both a severe and very mild phenotype.     

Perspectives and diagnostic considerations in spinal muscular atrophy

Spinal muscular atrophy is an autosomal recessive neurodegenerative disease and the most common genetic cause of infant mortality. The disease results in motor neuron loss and skeletal muscle atrophy. Spinal muscular atrophy is caused by mutations in the telomeric copy of the survival motor neuron 1 (SMN1) gene, but all patients retain a centromeric copy of the gene, SMN2. In the majority of cases, the disease severity correlates inversely with an increased SMN2 gene copy number. Because spinal muscular atrophy is both a severe and common disorder, a direct carrier testing has been beneficial to many families. The survival motor neuron protein is ubiquitously expressed and performs a role in the assembly of the spliceosome. It is still not understood why mutations in the SMN1 gene only seem to affect motor neurons. Progress has been made by developing therapeutic strategies based on understanding the pathogenesis of the disease. This review attempts to highlight some of the recent advances in the understanding of the disease with a focus on molecular diagnostics.     

Carrier testing for spinal muscular atrophy

Spinal muscular atrophy is the most common fatal hereditary disease among newborns and infants. There is as yet no effective treatment. Although a carrier test is available, currently there is disagreement among professional medical societies who proffer standards of care as to whether or not carrier screening for spinal muscular atrophy should be offered as part of routine reproductive care. This leaves health care providers without clear guidance. In fall 2009, a meeting was held by National Institutes of Health to examine the scientific basis for spinal muscular atrophy carrier screening and to consider the issues that accompany such screening. In this article, the meeting participants summarize the discussions and conclude that pan-ethnic carrier screening for spinal muscular atrophy is technically feasible and that the specific study of implementing a spinal muscular atrophy carrier screening program raises broader issues about determining the scope and specifics of carrier screening in general.     

Evaluation of humoral and cell-mediated inducible immunity to Haemophilus ducreyi in an animal model of chancroid.

To study the mechanisms of inducible immunity to Haemophilus ducreyi infection in the temperature-dependent rabbit model of chancroid, we conducted passive immunization experiments and characterized the inflammatory infiltrate of chancroidal lesions. Polyclonal immunoglobulin G was purified from immune sera raised against H. ducreyi 35000 whole-cell lysate or a pilus preparation and from naive control rabbits. Rabbits were passively immunized with 24 or 48 mg of purified polyclonal immunoglobulin G intravenously, followed 24 h after infusion by homologous titered infectious challenge. Despite titratable antibody, no significant difference in infection or disease was observed. We then evaluated the immunohistology of lesions produced by homologous-strain challenge in sham-immunized rabbits and those protectively vaccinated by pilus preparation immunization. Immunohistochemical stains for CD5 and CD4 T-lymphocyte markers were performed on lesion sections 4, 10, 15, and 21 days from infection. Lesions of pilus preparation vaccinees compared with those of controls had earlier infiltration with significantly more T lymphocytes (CD5+) and with a greater proportion of CD4+ T lymphocytes at day 4 (33% +/- 55% versus 9.7% +/- 2%; P = 0.002), corroborating earlier sterilization (5.0 +/- 2 versus 13.7 +/- 0.71 days; P < 0.001) and lesion resolution. Intraepithelial challenge of pilus-vaccinated rabbits with 100 micrograms of the pilus preparation alone produced indurated lesions within 48 h with lymphoid and plasmacytoid infiltration, edema, and extravasation of erythrocytes. We conclude that passive immunization may not confer a vaccine effect in this model and that active vaccination with a pilus preparation induces a delayed-type hypersensitivity skin test response and confers protection through cell-mediated immunity seen as an amplified lymphocytic infiltrate and accelerated maturation of the T-lymphocyte response.     

脊髓性肌萎缩患儿的NAIP基因分析

目的探讨脊髓性肌萎缩的基因型与临床表型（ｓｕｒｖｉｖａｌｍｏｔｏｒｎｅｕｒｏｎｅ,ＳＭＮ）的关系。方法应用ＰＣＲ技术对１３例运动神经元型基因缺失的脊髓性肌萎缩患儿进一步进行神经原性细胞凋亡抑制蛋白（ｎｅｕｒｏｎａｌａｐｏｐｔｏｓｉｓｉｎｈｉｂｉｔｏｒｙｐｒｏｔｅｉｎＮＡＩＰ）基因分析（Ⅰ型５例,Ⅱ型４例,Ⅲ型４例）。结果２例Ⅰ型患儿携有ＮＡＩＰ基因缺失（２／５,４０％）。结论ＮＡＩＰ基因缺失可能与脊髓性肌萎缩的临床表型严重程度有关     

Prenatal prediction of spinal muscular atrophy.

Spinal muscular atrophy (SMA) is a common cause of inherited morbidity and mortality in childhood. The wide range of phenotypes in SMA, uncertainty regarding its mode of inheritance, and the suggestion of linkage heterogeneity have complicated the genetic counselling of parents of affected children. The locus responsible for autosomal recessive SMA has been mapped to 5q11.2-q13.3. The most likely order of loci is cen-D5S6-(SMA,D5S125)-(JK53CA1/2,D5S112)-D5S3 9-qter, with highly polymorphic loci being identified at JK53CA1/2 and D5S39. We describe linkage studies with another highly polymorphic locus, D5S127, that is closely linked to D5S39. This genetic map can be used as the basis for genetic counselling in families with autosomal recessive SMA. Appropriate allowance can be made for sporadic cases owing to non-inherited causes and for linkage heterogeneity or misdiagnoses.     

Preimplantation genetic diagnosis of spinal muscular atrophy

After Duchenne muscular dystrophy, spinal muscular atrophy (SMA) is the most common severe neuromuscular disease in childhood. Since 1995, homozygous deletions in exon 7 of the survival motor neuron (SMN) gene have been described in >90-95% of SMA patients. However, the presence of a highly homologous SMN copy gene complicates the detection of exon 7 deletions. This paper describes the adjustment and evaluation of an established SMN exon 7 polymerase chain reaction (PCR) protocol at the single cell level, and the first preimplantation genetic diagnosis (PGD) of SMA with this PCR protocol. To determine PCR efficiency and allelic loss, 200 leukocytes of normal individuals, SMA carriers and patients, and 25 blastomeres were tested. The PCR efficiency of the SMN exon 7 and the adjacent copy gene sequence, tested in the leukocytes, were 90% and 91% respectively. No allelic loss was detected. One out of 25 blastomeres tested revealed a negative PCR signal for the SMN exon 7 sequence. All 25 showed the copy gene sequence. PGD of SMA was offered to a couple with an affected child homozygous for the SMN exon 7 deletion. After intracytoplasmic sperm injection, four and five embryos could be genotyped for the SMN exon 7 in two cycles respectively. After embryo transfer in the second PGD cycle an ongoing gemelli pregnancy was achieved. This study demonstrates that PGD for SMA is feasible when a previous child is homozygous for the SMN exon 7 deletion.      

Distal infantile spinal muscular atrophy associated with paralysis of the diaphragm: a variant of infantile spinal muscular atrophy

We report the clinical, electrophysiological, and morphological observations of five infants with an unusual form of spinal muscular atrophy (SMA). In these infants muscular weakness and atrophy were initially restricted to the distal limbs and this pattern was associated with paralysis of the diaphragm. The difference between the clinical manifestations of this syndrome and the classical form of infantile spinal muscular atrophy (SMA type 1) as well as other congenital hereditary neuropathies is discussed.     

脊髓性肌萎缩症的临床实践指南

脊髓性肌萎缩症(spinal muscular atrophy,SMA)为最常见的婴幼儿致死性常染色体隐性遗传病之一,由运动神经元存活基因1(SMN1)突变所致,新生儿发病率为1/10000〜1/6000,人群携带率约为1/72〜1/47,且具有种族差异性。临床表现为进行性、对称性、以肢体近端为主的肌无力和肌萎缩,根据发病时间与临床表型又分为Ⅰ〜Ⅳ型。约95%的SMA患者是由于SMN1基因第7外显子的纯合缺失所致。患者表型差异大、SMN1基因拷贝数变化多、存在假基因干扰、人群携带率高等因素,给SMA的早期诊断、遗传咨询、治疗和预防造成了较大的闲难。本指南总结了国内外的相关研究和指南共识,并结合中国人群的实际情况,介绍了SMA患者的临床表现和发病机制,总结了诊断与遗传咨询等方面的相关经验,期望对临床医师及相关工作者有所帮助,以促进SMA的规范诊治,降低患儿的出生率。