Impaired multimerization of human adiponectin mutants associated with diabetes. Molecular structure and multimer formation of adiponectin

Adiponectin is an adipocyte-derived hormone, which has been shown to play important roles in the regulation of glucose and lipid metabolism. Eight mutations in human adiponectin have been reported, some of which were significantly related to diabetes and hypoadiponectinemia, but the molecular mechanisms of decreased plasma levels and impaired action of adiponectin mutants were not clarified. Adiponectin structurally belongs to the complement 1q family and is known to form a characteristic homomultimer. Herein, we demonstrated that simple SDS-PAGE under non-reducing and non-heat-denaturing conditions clearly separates multimer species of adiponectin. Adiponectin in human or mouse serum and adiponectin expressed in NIH-3T3 or Escherichia coli formed a wide range of multimers from trimers to high molecular weight (HMW) multimers. A disulfide bond through an amino-terminal cysteine was required for the formation of multimers larger than a trimer. An amino-terminal Cys-Ser mutation, which could not form multimers larger than a trimer, abrogated the effect of adiponectin on the AMP-activated protein kinase pathway in hepatocytes. Among human adiponectin mutations, G84R and G90S mutants, which are associated with diabetes and hypoadiponectinemia, did not form HMW multimers. R112C and I164T mutants, which are associated with hypoadiponectinemia, did not assemble into trimers, resulting in impaired secretion from the cell. These data suggested impaired multimerization and/or the consequent impaired secretion to be among the causes of a diabetic phenotype or hypoadiponectinemia in subjects having these mutations. In conclusion, not only total concentrations, but also multimer distribution should always be considered in the interpretation of plasma adiponectin levels in health as well as various disease states.

The genetics of adiponectin

Adiponectin encoded by the APMI gene is one of the adipocyte-expressed proteins that function in the homeostatic control of glucose, lipid, and energy metabolism. Its dysregulation has been suggested to be involved in disorders covering the metabolic X syndrome, such as insulin resistance, obesity, type 2 diabetes, and coronary artery disease. Recent data present evidence of a genetic modulation of the adiponectin level, and linkage of the 3q27 locus, where the APMI gene lies, with diabetes and features of the metabolic X syndrome playing a putative role of the APMI gene in this syndrome. In this article, we present an overview of the results available to date and discuss positive evidence for a role of genetic variants of the APMI gene and questions that genetic data raise.

A new locus for spinocerebellar ataxia (SCA21) maps to chromosome 7p21.3-p15.1

We investigated a French family with a new type of autosomal dominant spinocerebellar ataxia that was excluded from all previously identified genes and loci. The patients exhibited a slowly progressive gait and limb ataxia variably associated with akinesia, rigidity, tremor, and hyporeflexia. A mild cognitive impairment also was observed in some cases. We performed a genomewide search and found significant evidence for linkage to chromosome 7p21.3-p15.1. Analysis of key recombinants and haplotype reconstruction traced this novel spinocerebellar ataxia locus to a 24cM interval flanked by D7S2464 and D7S516.

Single-nucleotide polymorphism haplotypes in the both proximal promoter and exon 3 of the APM1 gene modulate adipocyte-secreted adiponectin hormone levels and contribute to the genetic risk for type 2 diabetes in French Caucasians

Adiponectin (ACRP30), an adipocyte-secreted protein encoded by the APM1 gene, is known to modulate insulin sensitivity and glucose homeostasis, those effects protecting obese mice from diabetes. Plasma adiponectin levels correlate well with insulin sensitivity in humans, and are decreased in both type 2 diabetes (T2D) and obesity. We screened for single-nucleotide polymorphisms (SNPs) the APM1 gene coding and 5' sequences in 40 French Caucasians: 12 SNPs and 4 rare non-synonymous mutations of exon 3 were detected. The 10 most frequent SNPs were genotyped in 1373 T2D and obese French Caucasian subjects and in all subjects available from 148 T2D multiplex families. The screening for rare mutations of exon 3 was extended to 1246 T2D and obese French subjects and to the members of the 148 T2D multiplex families. A haplotype including SNPs -11391 and -11377, both located in the 5' sequences, was associated with adiponectin levels (P<0.0001) and with T2D (P=0.004). The presence of at least one non-synonymous mutation in exon 3 showed evidence of association with adiponectin levels (P=0.0009) and with T2D (P=0.005). We failed to detect an association with insulin resistance indexes. Although family-based association analysis with T2D did not reach significance, our results suggest that an at-risk haplotype of common variants located in the promoter and rare mutations in exon 3 contribute to the variation of the adipocyte-secreted adiponectin hormone level, and may be part of the genetic determinants for T2D in the French Caucasian population.

Positional candidate gene analysis of Lim domain homeobox gene (Isl-1) on chromosome 5q11-q13 in a French morbidly obese population suggests indication for association with type 2 diabetes

The Lim domain homeobox gene (Isl-1) is a positional candidate gene for obesity that maps on chromosome 5q11-q13, a locus linked to BMI and leptin levels in French Caucasians. Isl-1 might be involved in body weight regulation and glucose homeostasis via the activation of proglucagon gene expression, which encodes for glucagon and glucagon-like peptides. By mutation screening of 72 obese subjects, we identified three single-nucleotide polymorphisms (SNPs) in the Isl1 gene. The allele frequencies in the morbidly obese group did not differ from that of the control group. In the obese group, the -47G allele was associated with a decreased risk of type 2 diabetes (odds ratio 0.41, P = 0.019). The AG bearers displayed a higher maximal BMI than the AA bearers in the whole obese group (P = 0.026) as well as in the type 2 diabetic obese subgroup (P = 0.014). In obese families, this allele was not preferentially transmitted from heterozygous parents to their obese siblings, indicating that Isl-1 does not contribute to the linkage with obesity on 5cen-q. However, in French Caucasian morbidly obese subjects, the Isl1-47A-->G SNP may modulate the risk for type 2 diabetes and may increase body weight in diabetic morbidly obese subjects.

Molecular and cytogenetic characterisation of a small interstitial de novo 20p13-->p12.3 deletion in a patient with severe growth deficit

We report on a small de novo interstitial deletion of the short arm of chromosome 20, 46,XY,del(20)(p12.3p13), in a young boy with hypotonia, moderate development delay, mild facial dysmorphism and severe growth failure. This patient did not show major features of Alagille-Watson Syndrome (AWS) which are common in more proximal 20p deletions. Standard and high resolution chromosome banding analysis revealed an apparent terminal deletion. Nevertheless, using chromosomal fluorescent in situ hybridization (FISH) and molecular analysis with polymorphic markers, we demonstrated that the abnormal chromosome resulted from a de novo interstitial deletion of paternal origin spanning from D20S842 to D20S900 and covering approximately 6 Mb. These findings indicate that a karyotype can lead to insufficient characterization of an apparently terminal deletion, and that one or a few genes in 20p13-->p12.3 bands are important for normal growth.

Mutation screening of the urocortin gene: identification of new single nucleotide polymorphisms and association studies with obesity in French Caucasians

A linkage between obesity-related phenotypes and the 2p21-23 locus has been reported previously. The urocortin (UCN) gene resides at this interval, and its protein decreases appetite behavior, suggesting that UCN may be a candidate gene for susceptibility to obesity. We localized the UCN gene by radiation hybrid mapping, and the surrounding markers were genotyped in a collection of French families. Evidence for linkage was shown between the marker D2S165 and leptin levels (LOD score, 1.34; P = 0.006) and between D2S2247 and the z-score of body mass index (LOD score, 1.829; P = 0.0019). The gene was screened for SNPs in 96 obese patients. Four new variants were established. Two single nucleotide polymorphisms were located in the promoter (-535 A-->G, -286 G-->A), one in intron 1 (+31 C-->G), and one in the 3'-untranslated region (+34 C-->T). Association studies in cohorts of 722 unrelated obese and 381 control subjects and transmission disequilibrium tests, performed for the two frequent promoter polymorphisms, in 120 families (894 individuals) showed that no association was present between these variants and obesity, obesity-related phenotypes, and diabetes. Thus, our analyses of the genetic variations of the UCN gene suggest that, at least in French Caucasians, they do not represent a major cause of obesity.

Scheduled kinetics of cell proliferation and phenotypic changes during immature thymocyte generation

Precursor CD4-CD8- (DN) thymocytes rearrange their TCR-beta genes, and only those which succeed in beta-selection subsequently expand and differentiate into immature CD4+CD8+ (DP) thymocytes. The cell subsets corresponding to the successive steps of this transition can be defined in terms of CD44 and CD25 expression. We partially synchronized the differentiation process by eliminating cycling cells with the anti-mitotic agent demecolcine. Using in vivo pulse labeling with bromodeoxyuridine, we determined the order of entry into DNA synthesis of the different DN and transitory (CD4-/lo CD8+) cell subsets. Two independent proliferation phases were identified. The first cells to enter the cell cycle were CD44-CD25lo, and CD4/CD8/TCR-/BrdU four-color staining showed that they all expressed a low density of the TCR-beta chain, an element of the pre-TCR (the TCR-alpha locus is still in germ-line configuration at this stage). Cycling of CD44+CD25+ cells was detected later, and no starting point was observed at the CD44-CD25hi stage. CD8 expression was immediately detectable in cycling cells, but they took 24 h to reach the DP stage. The study of TCR-Calpha-deficient mice showed that beta gene rearrangement occurred once proliferation had ceased at the DP stage, and that it had no influence on the DN-DP transition. These data show that precursor thymocytes undergo two independent waves of expansion, and that the second wave is restricted to cells capable of pre-TCR expression.

Routine mutation screening of HNF-1alpha and GCK genes in MODY diagnosis: how effective are the techniques of DHPLC and direct sequencing used in combination?

AIMS/HYPOTHESIS

Mutations in the hepatocyte nuclear factor (HNF)-1alpha and glucokinase (GCK) genes are the major causes of monogenic forms of Type II (non-insulin-dependent) diabetes mellitus (Maturity-Onset Diabetes of the Young subtypes, MODY). We evaluated the effectiveness of fluorescent single-strand conformation polymorphism (F-SSCP), denaturing high-performance liquid chromatography (DHPLC) and sequencing based mutation detection in the molecular diagnosis of MODY. Our goal is to identify a rapid, efficient and cost effective mutation detection method for the molecular diagnosis of MODY and other human genetic disorders.

METHODS

We evaluated the accuracy of DHPLC in screening for MODY 2 and 3 mutations. In addition, we compared the sensitivity, specificity, cost, handling time and analysis time of fluorescent single-strand conformation polymorphism, denaturing high-performance liquid chromatography and direct sequencing screening methods.

RESULTS

Denaturing high-performance liquid chromatography is a recently developed method for mutation detection. It is cost effective, powerful and reliable and quite suitable for 22 out of the 24 fragments required for MODY 2 and 3 testing. However, exons 1 and 7 of the HNF-1alpha gene are very polymorphic and so direct sequencing is faster as well as more efficient and reliable.

CONCLUSION/INTERPRETATION

Our results suggest that combining denaturing high-performance liquid chromatography and direct sequencing is a good approach for the routine detection of HNF-1alpha and GCK mutations in MODY families. Denaturing high-performance liquid chromatography appears to be a powerful tool in genetic testing and the method could be applied to the molecular diagnosis of other human genetic diseases.

Linkage and association studies between the proopiomelanocortin (POMC) gene and obesity in caucasian families

AIMS/HYPOTHESIS

The region 2p21-23, containing the proopiomelanocortin gene (POMC), was reported to be linked to leptin concentrations in Mexican-American, French and African-American cohorts. A polyhormone peptide, POMC is expressed in brain, gut, placenta and pancreas. The POMC mutations are responsible for rare cases of early-onset obesity. Thus we examined the contribution of the POMC locus to obesity in French families.

METHODS

Single and multipoint linkage studies were done between obesity, obesity associated-phenotypes (leptin values and z-score of the body mass index) and three newly mapped markers surrounding POMC in 264 affected sib-pairs from French obese families. Mutation screening of the exons and intron/exon junctions of the POMC gene was realised by direct sequencing. Association studies were done in 379 unrelated obese patients and 370 non-obese non-diabetic subjects.

RESULTS

Linkage analysis confirmed the trend towards linkage between polymorphic markers around POMC and variations of leptin concentrations and z-score (maximum lod score at D2S2337 = 2.03). Mutation screening of the POMC gene in the French Caucasian cohort identified two previously reported polymorphisms. None of these variants was associated with obesity, diabetes or serum leptin and lipid concentrations.

CONCLUSION/INTERPRETATION

Our results indicate that mutations in the POMC gene do not contribute to the variance of obesity associated phenotypes, at least in French Caucasians. Given the replicated evidence of linkage between leptin values and the chromosome 2p21-23 region in different populations, it is likely that functional variant(s) in the POMC regulating sequences or in an unknown gene in this region explains this linkage.

An uncoupling protein 3 gene polymorphism associated with a lower risk of developing Type II diabetes and with atherogenic lipid profile in a French cohort

AIMS/HYPOTHESIS

The UCP2-UCP3 gene region has been previously associated with obesity and diabetes. In a large representative cohort of Northern France (MONICA project), we studied the effect of a recently reported C/T polymorphism located in the 5' sequences of the UCP3 gene on anthropometric measurements and lipid profile. We also examined the association of this polymorphism with obesity and Type II (non-insulin-dependent) diabetes mellitus.

METHODS

The -55 C/T polymorphism of the UCP3 gene has been genotyped in 1155 subjects from the MONICA project. Association studies were done with diabetes, obesity and related phenotypes. Results were ascertained in a second cohort of well-characterized Type II diabetic and control subjects.

RESULTS

The variant T allele was associated with a decreased risk of developing Type II diabetes. Frequencies of the T allele were 13.3% compared with 22%, p = 0.04, in the diabetic and control groups, respectively. This observation was confirmed in the second cohort of French Type II diabetic (n = 171) and control (n = 124) subjects: 17.8% compared with 25%, p = 0.03. Moreover, subjects bearing the TT genotype had higher plasma total cholesterol and LDL-cholesterol concentrations (p = 0.0006 and p = 0.001, respectively) than subjects bearing wild or heterozygous genotypes.

CONCLUSION/INTERPRETATION

The UCP3 -55 C/T polymorphism was associated with a higher atherogenic profile and modified the risk for the development of Type II diabetes.

Selective involvement of the Fas (CD95)/Fas ligand pathway in bone marrow B cell progenitors

B lymphocyte generation in bone marrow (BM) compensates for cell loses. The Fas / Fas ligand (FasL) pathway has been implicated in apoptosis of various cell types. Abnormalities of the Fas receptor or of FasL expression are associated with excessive T cell proliferation and autoimmunity. To examine the role of the Fas / FasL system in B cell differentiation, we created double-chimeric mice by transferring both C57BL / 6 (B6)-Fas(+) and lpr-FasL(+) BM cells into RAG-2(- / -) hosts. Equal numbers of stem cells were co-injected into sublethally irradiated recipients, and their progeny were studied by using antibodies directed against the B6-Ly5. 1(+)5.2(+) and lpr-Ly5.1(-)5.2(+) populations. A longitudinal study lasting for up to 6 months revealed that cells of the lpr phenotype dominated the B6 phenotype in the BM, as a result of their active proliferation. Analysis of the B cell compartment showed more lpr than B6 cells among immature HSA(hi)B220(lo) populations. In contrast, the lpr and B6 phenotypes were equally represented among mature B cells. BM transfer to second hosts indicated that B6-derived B cell progenitors were absent from the first host. These data suggest that activation of the Fas / FasL pathway disturbs the early steps of B cell development and might therefore contribute to the onset of autoimmune disorders.

Regulation and kinetics of premigrant thymocyte expansion

Normal mature thymocytes proliferate before emigrating to the periphery, and continuous bromodeoxyuridine labeling showed that more than 30 % of fully mature thymic emigrants have replicated DNA in the 24 h before exit. The percentage of DNA-synthetizing single-positive (SP) thymocytes is transiently augmented during the postnatal period, with peaks on days 2 and 4 for CD4 and CD8 cells, respectively. Similar kinetics were observed in mouse chimeras made by transfer of normal bone marrow cells into RAG-2-deficient mice. These data show that proliferation of mature thymocytes is developmentally regulated. The proliferation peaks (on days 16 and 18 post transfer) observed in simple bone marrow chimeras were abolished when lymph node T cells were mixed with the bone marrow cell inoculum, suggesting that the peripheral pool controls the late thymic expansion. The phenotype of cycling SP thymocytes is atypical: they do not regulate activation and adhesion surface molecules like peripheral activated T cells.

A genetic variation in the 5' flanking region of the UCP3 gene is associated with body mass index in humans in interaction with physical activity

AIMS/HYPOTHESIS

In obese French Caucasian subjects we previously described a silent UCP3 Tyr99Tyr mutation, associated with body mass index. We hypothesised that an unknown polymorphism in the vicinity of the gene could contribute to obesity.

METHODS

Morbidly obese subjects were screened for mutations in 1 kb upstream from the UCP3 gene. Association studies were done between a variant and obesity in 401 morbidly obese and 231 control subjects.

RESULTS

We detected three rare genetic variants and one polymorphism: a +5 G-->A in exon 1, a -155 C-->T, a -439 A insertion and a -55 C-->T located 6 bp from the putative TATA box. This variant was in linkage disequilibrium with the Tyr99Tyr polymorphism. Frequencies of the variant allele at the -55 locus were similar in the obese and control groups (0.23 vs 0.21). The -55 polymorphism was associated with BMI in the obese group (p = 0.0031): BMI was higher in TT than in CC or CT patients. Likewise control subjects with a TT genotype had a higher BMI (p = 0.03). In the obese group, homozygosity for this variant is a risk factor for high BMI (odds ratio: 1:75, p = 0.02). Obese patients were divided into tertiles according to physical activity. In the group with a wild C/C genotype, BMI was negatively associated with physical activity (p = 0.015).

CONCLUSION/INTERPRETATION

The C-->T polymorphism in the 5' sequences of the UCP3 gene might contribute to the corpulence in obese and normal weight subjects and alter the benefit of physical activity. The UCP3 gene can be considered as a gene modifying corpulence.

Increased fetal and extramedullary hematopoiesis in Fas-deficient C57BL/6-lpr/lpr mice

In this study, we examined the consequences of Fas deficiency on hematopoiesis in C57BL/6-lpr/lpr mice. We found a striking extramedullary increase in hematopoietic progenitor cells, comprising erythroid and nonerythroid lineages alike. These modifications preceded the lymphadenopathy, because early progenitors (colony-forming units-spleen [CFU-S] day 8) were already augmented in day-18 fetal livers of the lpr phenotype. Three weeks after birth, CFU-S increased in peripheral blood and spleen and colony-forming cells (CFU-C) began to accumulate 1 to 3 weeks later. Extramedullary myelopoiesis augmented progressively in Fas-deficient mice, reaching a maximum within 6 months. By then, mature and immature myeloid cells had infiltrated the spleen, the liver, and the peritoneal cavity. Similar changes occurred in C57BL/6-gld/gld mice, indicating that they resulted from Fas/FasL interactions. Medullary hematopoiesis was not significantly modified in adult mice of either strain. Yet, the incidence of CFU-S decreased after Fas cross-linking on normal bone marrow cells in the presence of interferon gamma, consistent with a regulatory function of Fas/FasL interactions in early progenitor cell development. These data provide evidence that Fas deficiency can affect hematopoiesis both during adult and fetal life and that these modifications occur independently from other pathologies associated with the lpr phenotype.

Distribution of cycling T lymphocytes in blood and lymphoid organs during immune responses

Proliferation of murine T lymphocytes in blood, lymph nodes, and spleen was studied in four in vivo stimulation systems, using BrdU pulse-labeling of DNA-synthesizing cells. The T cell response to the superantigen Staphylococcus enterotoxin B (SEB) was studied in detail. Vbeta8+ T cells showed a peak of DNA synthesis 16-24 h after SEB injection, and the percentage of BrdU+ CD4 and CD8 T cells was higher in blood than in lymph nodes and spleen. DNA synthesis was preceded by massive migration of Vbeta8+ cells from blood to lymphoid organs, in which the early activation marker CD69 was first up-regulated. SEB-nonspecific Vbeta6+ cells showed minimal stimulation but, when cycling, also expressed a high level of CD69. The other systems studied were injection of the IFN-gamma inducer polyinosinic:polycytidylic acid, infection by the BM5 variants of murine leukemia virus (the causative agent of murine AIDS), and T cell expansion after transfer of normal bone marrow and lymph node cells into recombinase-activating gene-2-deficient mice. In each case, a peak of T cell proliferation was observed in blood. These data demonstrate the extensive redistribution of cycling T cells in the first few hours after activation. Kinetic studies of blood lymphocyte status appear crucial for understanding primary immune responses because cycling and redistributing T lymphocytes are enriched in the circulating compartment.

Excision repair defect in Rothmund Thomson syndrome

Rothmund Thomson syndrome is a rare autosomal recessive skin disorder. The main clinical feature is poikiloderma appearing in early childhood associated with skeletal abnormalities. Early occurrence of malignancies is another relevant feature. Here we describe the clinical features of 2 patients with Rothmund Thomson syndrome who were investigated for the in vitro DNA repair capacities of blood cells following UVC radiation exposure. DNA excision repair, assessed with unscheduled DNA synthesis following UVC exposure, was decreased in both patients. Such a defect might explain the patients' sensitivity to sunlight and the relatively high risk of cancer associated with this syndrome.

Cytogenetics in multiple myeloma: a multicenter study of 24 patients with t(11;14)(q13;q32) or its variant

Twenty-two patients with multiple myeloma (MM) with a classical t(11;14)(q13;q32) and two complex variants also involving 11q13 and 14q32 regions are reported. We show that t(11;14) (q13;q32) is predominantly noticed in stages II and III and never in stage I patients. Translocation (11;14)(q13;q32) is predominantly observed in hypodiploid or pseudodiploid clones associated with total or partial monosomy of chromosome 13 and additional structural changes in chromosome 1. These translocations may be discovered not only in standard cultures (24-48 hours) without stimulation, but also in cytokine-stimulated cultures (granulocyte macrophage colony-stimulating factor and interleukin 6). The t(11;14)(q13;q32) as a primary or secondary event in MM is discussed, because, in one patient, it was only discovered at relapse.

Regulatory CD4 T cells: expression of IL-2R alpha chain, resistance to clonal deletion and IL-2 dependency

We recently characterized a CD4+ T cell population expressing the IL-2R alpha chain (CD25), producing IL-10 and resisting clonal deletion induced by viral superantigen (vSAG) encoded by mouse mammary tumor virus [MMTV(SW)]. We now report that these apoptosis-resistant cells are generated in the thymus but not from the immature CD4+ CD8+ thymocytes. They migrate from the thymus and are found in the periphery from at least the 10th day of life, after which they expand with the same kinetics in normal and MMTV(SW)-infected mice. Their strong capacity for expansion in the periphery makes this population insensitive to thymectomy in adulthood. CD4+ CD25+ cells were totally dependent on exogenous IL-2 for growth in vitro and in vivo, and were missing in IL-2 knockout (KO) mice. The absence of this population and/or an inability to produce IL-10 may be the missing link between IL-2R alpha KO, IL-2 KO and IL-10 KO mice, which all die of inflammatory bowel disease.

Expansion of mature thymocyte subsets before emigration to the periphery

A small population of DNA-synthesizing mature thymocytes could be defined by analyzing cell surface markers and 5-bromo-2'-deoxyuridine (BrdUrd) labeling by four-color cytofluorometry. These cells have a completely mature phenotype (CD4- CD8+ or CD4+ CD8- TCR(high), HSA-, Qa-2(high)) and expand only weakly after BrdUrd incorporation. They recovered immediately in total number and in DNA synthesis rate after treatment with the antimitotic drug demecolcin, thus much faster than immature CD4+ CD8+ thymocytes. These data demonstrate the existence of a late intrathymic expansion phase, independent of that of developing CD4+ CD8+ immature cells, and involving phenotypically mature cells renewed each day. In mixed chimeras prepared by transfer of bone marrow and lymph node cells into RAG-2(-/-) mice, all cycling mature thymocytes were bone marrow derived. They are thus produced in situ and do not correspond to peripheral T cells reentering the thymus. Double FITC/BrdUrd detection showed that a high proportion (10-20%) of recent thymic emigrants were BrdUrd+ just postcycling cells and that around 50% of cycling mature thymocytes are just ready to emigrate to the periphery in the few hours after DNA synthesis. The late intrathymic expansion phase demonstrated here increases the daily thymic cell export by at least 30%. It could play a role in the adjustment of the T cell repertoire before emigration and in the regulation of the thymic cell output into the peripheral T cell pool.

Expansion of mature thymocyte subsets before emigration to the periphery

A small population of DNA-synthesizing mature thymocytes could be defined by analyzing cell surface markers and 5-bromo-2'-deoxyuridine (BrdUrd) labeling by four-color cytofluorometry. These cells have a completely mature phenotype (CD4- CD8+ or CD4+ CD8- TCR(high), HSA-, Qa-2(high)) and expand only weakly after BrdUrd incorporation. They recovered immediately in total number and in DNA synthesis rate after treatment with the antimitotic drug demecolcin, thus much faster than immature CD4+ CD8+ thymocytes. These data demonstrate the existence of a late intrathymic expansion phase, independent of that of developing CD4+ CD8+ immature cells, and involving phenotypically mature cells renewed each day. In mixed chimeras prepared by transfer of bone marrow and lymph node cells into RAG-2(-/-) mice, all cycling mature thymocytes were bone marrow derived. They are thus produced in situ and do not correspond to peripheral T cells reentering the thymus. Double FITC/BrdUrd detection showed that a high proportion (10-20%) of recent thymic emigrants were BrdUrd+ just postcycling cells and that around 50% of cycling mature thymocytes are just ready to emigrate to the periphery in the few hours after DNA synthesis. The late intrathymic expansion phase demonstrated here increases the daily thymic cell export by at least 30%. It could play a role in the adjustment of the T cell repertoire before emigration and in the regulation of the thymic cell output into the peripheral T cell pool.

Delayed spontaneous alternation in intact and cerebellectomized control and lurcher mutant mice: differential role of cerebellar cortex and deep cerebellar nuclei

Lurcher mutant (+/Lc) mice exhibit a massive loss of neurons in the cerebellar cortex and in the inferior olivary nucleus while deep cerebellar nuclei are essentially intact. To discriminate the respective participation of the cerebellar cortex and deep structures in learning and memory, the authors subjected 3- to 6-month-old +/Lc mice to a delayed spontaneous alternation task to test their working and long-term spatial memories. Results show that wild type (+/+) mice alternated above chance even after a 1-hr delay between the forced and choice trials, whereas in +/Lc mice, long-term memory was impaired. Cerebellectomized +/+ mice behave as +/Lc mice (working memory was preserved but long-term memory was not), whereas in the cerebellectomized +/Lc mice, both working and long-term memories were altered. These results are discussed in terms of relationships between the cerebellum and the hippocampus.

In vivo T cell response to viral superantigen. Selective migration rather than proliferation

Superantigens induce T cell activation and proliferation in vitro, and some also induce cell activation in vivo. MMTV(SW) is an infectious mouse mammary tumor virus (MMTV) encoding a superantigen with the same Vbeta specificity as MIs-1a (Mtv-7), which induces a strong local response in vivo. injection of MMTV(SW) into mouse footpads leads to accumulation of superantigen-reactive T cells (Vbeta6+CD4+) and B cells in the draining lymph nodes (LN). We investigated the kinetics of this cell accumulation by measuring cell activation (blastogenesis, CD25 and CD69 expression), cell migration (using syngenic FITC-labeled CD4+ cells and L-selectin detection), and cell proliferation (using in vivo labeling with bromodeoxyuridine). Specific T cells selectively migrated to the draining LN. Accumulating Vbeta6+CD4+ T cells were large CD69+ cells, but remained CD25 negative and showed down-regulated L-selectin expression. Their DNA synthesis rate, studied by pulse labeling and continuous administration of bromodeoxyuridine, was increased, but remained too low to explain the draining LN hyperplasia. These data show that the local T cell response to MMTV(SW) mainly consists of selective migration followed by local activation of reactive T cells, and that cell proliferation is only a minor component of the response. By contrast, the optimal dose of staphylococcal enterotoxin B that, nevertheless, leads to a lower reactive T cell accumulation in the draining LN induces a very high proliferation rate.

In vivo T cell response to viral superantigen. Selective migration rather than proliferation

Superantigens induce T cell activation and proliferation in vitro, and some also induce cell activation in vivo. MMTV(SW) is an infectious mouse mammary tumor virus (MMTV) encoding a superantigen with the same Vbeta specificity as MIs-1a (Mtv-7), which induces a strong local response in vivo. injection of MMTV(SW) into mouse footpads leads to accumulation of superantigen-reactive T cells (Vbeta6+CD4+) and B cells in the draining lymph nodes (LN). We investigated the kinetics of this cell accumulation by measuring cell activation (blastogenesis, CD25 and CD69 expression), cell migration (using syngenic FITC-labeled CD4+ cells and L-selectin detection), and cell proliferation (using in vivo labeling with bromodeoxyuridine). Specific T cells selectively migrated to the draining LN. Accumulating Vbeta6+CD4+ T cells were large CD69+ cells, but remained CD25 negative and showed down-regulated L-selectin expression. Their DNA synthesis rate, studied by pulse labeling and continuous administration of bromodeoxyuridine, was increased, but remained too low to explain the draining LN hyperplasia. These data show that the local T cell response to MMTV(SW) mainly consists of selective migration followed by local activation of reactive T cells, and that cell proliferation is only a minor component of the response. By contrast, the optimal dose of staphylococcal enterotoxin B that, nevertheless, leads to a lower reactive T cell accumulation in the draining LN induces a very high proliferation rate.

Thymic medulla epithelial cells acquire specific markers by post-mitotic maturation

The development of thymocyte subsets and of the thymic epithelium in SCID and RAG-2/-mice was monitored after normal bone-marrow-cell transfer. The kinetics of thymic reconstitution and their relationships with cell proliferation were investigated by using bromodeoxyuridine to detect DNA-synthesizing cells among lymphoid cells by 3-color flow cytometry, and in epithelial compartments by staining frozen sections. Thymocytes started to express CD8 and CD4 10 days after transfer, simultaneously with extensive proliferation. The first mature CD4+ single-positive cells were generated, from resting CD4+CD8+ cells after day 15. During this day 10-15 period, many epithelial cells positive for cortex-specific or panepithelial markers were labeled with BrdUrd after pulse-injection. Organized medullary epithelium also developed after day 15, that is, synchronously with the appearance of mature thymocytes, but medullary cells were never found BrdUrd+. These results suggest that, in these models, the reconstitution of the thymic epithelial network proceeds through expansion of preexisting cortical or undifferentiated cells and by later maturation (acquisition of specific markers) of medullary cells. This last process is dependent of the presence of mature thymocytes.

Keratoderma with scleroatrophy of the extremities or sclerotylosis (Huriez syndrome): a reappraisal

Keratoderma with scleroatrophy of the extremities, also referred to as Huriez syndrome, is a rare, autosomal dominant condition, first described in 42 of 132 members of two families from northern France. The term sclerotylosis was proposed because of the pseudosclerodermatous appearance of the hands and digits. The distinctive feature of this syndrome is the risk of the development of squamous cell carcinoma on affected skin. Since the initial description of this disease, three other families, and possibly a fourth, have been reported. In the present study, we reassessed the clinical, pathological and genetic data in 114 members of one of the two original families, of whom 27 were affected by this syndrome.

Differential roles of cerebellar cortex and deep cerebellar nuclei in the learning of the equilibrium behavior: studies in intact and cerebellectomized lurcher mutant mice

Three- to 6-month-old lurcher mutant mice (+/lc), which exhibit a massive loss of neurons in the cerebellar cortex and in the inferior olivary nucleus but whose deep cerebellar nuclei are essentially intact, were trained daily, for 9 days, to maintain their equilibrium upon a rota rod rotating at 20 or 30 revolutions per minute (rpm). Their scores were measured and their behavior upon the rotating rod quantified in comparison to those of matched control (+/+) mice. Lurcher mice were able to learn to maintain their equilibrium efficiently when rotated at 20 rpm but were not when rotated at 30 rpm. After cerebellectomy, the equilibrium capabilities of the animals were much altered, especially in +/lc. These results show that the deep cerebellar nuclei are sufficient for motor learning, provided the task is not too difficult (20 rpm), but that the cerebellar cortex is required when the task is more difficult (30 rpm). Therefore, it can be concluded that the adaptive motor capabilities of lurcher mice are less developed than those of control animals.

Cell expansion and growth arrest phases during the transition from precursor (CD4-8-) to immature (CD4+8+) thymocytes in normal and genetically modified mice

T cell early precursors belong to the CD3-CD4-CD8- triple negative (TN) thymocyte population that can be subdivided on the basis of CD44, CD25, and heat-stable Ag (HSA) expression. The kinetics and precursor product relationships of these subsets, as well as of the CD4/8low intermediates, were studied by using pulse labeling with bromodeoxyuridine (BrdUrd). The highest frequencies of DNA-synthesizing cells were found in CD44+CD25+ and CD44-CD25low or CD25- subsets. The major TN cell type (CD44-CD25high), as well as CD44+ CD25-HSAlow early precursors, contained a majority of resting cells. RAG-2-/- mice contained less cells in DNA synthesis than normal mice, and CD44-CD25-/low cells were absent. In female mice transgenic for the anti-HYTCR, CD44-CD25high cells were almost all cycling, but a high percentage of resting cells was found in CD44-CD25- cells. In days following the BrdUrd pulse, there was a reduction in the number of BrdUrd+ cells in most subsets, with the exception of the labeled CD44-CD25high cells that showed a bell-shaped curve. The kinetics and cell size evolution suggest that the majority of these cells do not give rise to CD4+CD8+ cells. In RAG-2-/- cells, the block at the CD44-CD25high stage involved all cells. In TCR transgenic (Tg) mice, no block was seen at the CD44-CD25high stage, suggesting that early expression of a complete TCR receptor precludes the normal selection step. However, another block in the differentiation process was observed at the CD44-CD25- step in TCR Tg mice, suggesting an additional selection point.

Cell expansion and growth arrest phases during the transition from precursor (CD4-8-) to immature (CD4+8+) thymocytes in normal and genetically modified mice

T cell early precursors belong to the CD3-CD4-CD8- triple negative (TN) thymocyte population that can be subdivided on the basis of CD44, CD25, and heat-stable Ag (HSA) expression. The kinetics and precursor product relationships of these subsets, as well as of the CD4/8low intermediates, were studied by using pulse labeling with bromodeoxyuridine (BrdUrd). The highest frequencies of DNA-synthesizing cells were found in CD44+CD25+ and CD44-CD25low or CD25- subsets. The major TN cell type (CD44-CD25high), as well as CD44+ CD25-HSAlow early precursors, contained a majority of resting cells. RAG-2-/- mice contained less cells in DNA synthesis than normal mice, and CD44-CD25-/low cells were absent. In female mice transgenic for the anti-HYTCR, CD44-CD25high cells were almost all cycling, but a high percentage of resting cells was found in CD44-CD25- cells. In days following the BrdUrd pulse, there was a reduction in the number of BrdUrd+ cells in most subsets, with the exception of the labeled CD44-CD25high cells that showed a bell-shaped curve. The kinetics and cell size evolution suggest that the majority of these cells do not give rise to CD4+CD8+ cells. In RAG-2-/- cells, the block at the CD44-CD25high stage involved all cells. In TCR transgenic (Tg) mice, no block was seen at the CD44-CD25high stage, suggesting that early expression of a complete TCR receptor precludes the normal selection step. However, another block in the differentiation process was observed at the CD44-CD25- step in TCR Tg mice, suggesting an additional selection point.

Stochastic coreceptor shut-off is restricted to the CD4 lineage maturation pathway

Kinetics of mature T cell generation in the thymus of normal or major histocompatibility complex (MHC) class I- or II-deficient mice were studied by the bromodeoxyuridine pulse labeling method. As previously described, the early activation and final maturation phases were found to be synchronous for the two T cell lineages, but CD4+8- cells were generated faster than CD4-8+ cells in MHC class I- and II-deficient mice, respectively. CD8 downregulation started on day 2 after cell proliferation even in the absence of MHC class II expression. CD8 downregulation thus appears to be stochastic at its beginning. By contrast, CD4 shut-off was found totally instructive, as the generation of CD4lo8+ cells with a high TCR density was not observed in class I-deficient mice. The analysis of the V beta 14 TCR frequencies in CD4/8 subsets in normal and MHC-deficient mice confirmed that CD4 and CD8 generation pathways are not symmetrical. These findings show that commitment towards the CD4+8- or CD4-8+ phenotype is controlled at the CD8lo step for the former and at the CD4+8+ double-positive stage for the latter.

Production, selection, and maturation of thymocytes with high surface density of TCR

The main steps in intrathymic T cell differentiation have been defined using bromodeoxyuridine as a postmitotic cell tracer. Thymocytes with a high surface expression of the TCR are generated in the first 24 h after DNA synthesis. The phenotype of these TCR(high) cells was studied during 10 days by using pairs of surface markers associated with BrdUrd. During the first 2 days, TCR(high) cells were of the CD4+CD8+HSA(high) phenotype, transiently expressed the early activation marker CD69, and contained a high percentage of cycling cells. This activation step preceded the transition from CD4+CD8+ to CD4+CD8- and then to CD4-CD8+ cells, followed by progressive HSA down regulation and increase in the expression of H-2K, Qa-2, and CD45RB. The phenotypic maturation was completed in 9 days. In Mls-1a mice, negative selection of V beta 6+ cells was observed at the earliest step of TCR(high) cell generation, and positive selection of V beta 8.2+ and V beta 14+ cells took place later and was correlated to the activation step. These data suggest that high TCR expression and cell activation are necessary for positive selection and subsequent T cell maturation.

Production, selection, and maturation of thymocytes with high surface density of TCR

The main steps in intrathymic T cell differentiation have been defined using bromodeoxyuridine as a postmitotic cell tracer. Thymocytes with a high surface expression of the TCR are generated in the first 24 h after DNA synthesis. The phenotype of these TCR(high) cells was studied during 10 days by using pairs of surface markers associated with BrdUrd. During the first 2 days, TCR(high) cells were of the CD4+CD8+HSA(high) phenotype, transiently expressed the early activation marker CD69, and contained a high percentage of cycling cells. This activation step preceded the transition from CD4+CD8+ to CD4+CD8- and then to CD4-CD8+ cells, followed by progressive HSA down regulation and increase in the expression of H-2K, Qa-2, and CD45RB. The phenotypic maturation was completed in 9 days. In Mls-1a mice, negative selection of V beta 6+ cells was observed at the earliest step of TCR(high) cell generation, and positive selection of V beta 8.2+ and V beta 14+ cells took place later and was correlated to the activation step. These data suggest that high TCR expression and cell activation are necessary for positive selection and subsequent T cell maturation.

[Familial thymoma and translocation t (14;20) (q24;p13)]

A familial lympho-epithelial thymoma with constitutional chromosomal translocation t (14;20) (q24;p13) is presented: the thymoma and its particular translocation are present in the mother and the two sons of her offspring. The small number of cases do not allow establishing any relation between thymoma and this particular translocation. Concerning genetic counseling, an annual thoracic radiography is necessary for all the other family members, carriers or not of the translocation.

Normal sequence of phenotypic transitions in one cohort of 5-bromo-2'-deoxyuridine-pulse-labeled thymocytes. Correlation with T cell receptor expression

"In vivo" kinetics of T cell differentiation and TCR expression in the normal murine thymus were re-evaluated using a new technique for simultaneous detection of bromodeoxyuridine and two surface markers. The transition from CD4-8- precursors to CD4+8+ immature cells was directly observed during cell proliferation, and shown to proceed through transitory intermediates expressing no or low amounts of CD4. CD3-TCR expression also started during this transition and resulted in the production of a majority of TCRlo cells but also of a significant number (1 to 2 x 10(6) of TCRhi immature (heat-stable Ag+) thymocytes. After cessation of proliferation, the maturational transition from CD4+8+ to CD4+8- and CD4-8+ (in this order) was restricted to TCRhi cells produced during CD4+8+ cell generation. The acquisition of the single positive phenotype preceded HSA down-regulation, suggesting that maturation of TCRhi thymocytes proceeds in two separate steps. The major TCRloCD4+8+ subset appeared a dead end subset and showed no up-regulation of TCR expression at any time.

Normal sequence of phenotypic transitions in one cohort of 5-bromo-2'-deoxyuridine-pulse-labeled thymocytes. Correlation with T cell receptor expression

"In vivo" kinetics of T cell differentiation and TCR expression in the normal murine thymus were re-evaluated using a new technique for simultaneous detection of bromodeoxyuridine and two surface markers. The transition from CD4-8- precursors to CD4+8+ immature cells was directly observed during cell proliferation, and shown to proceed through transitory intermediates expressing no or low amounts of CD4. CD3-TCR expression also started during this transition and resulted in the production of a majority of TCRlo cells but also of a significant number (1 to 2 x 10(6) of TCRhi immature (heat-stable Ag+) thymocytes. After cessation of proliferation, the maturational transition from CD4+8+ to CD4+8- and CD4-8+ (in this order) was restricted to TCRhi cells produced during CD4+8+ cell generation. The acquisition of the single positive phenotype preceded HSA down-regulation, suggesting that maturation of TCRhi thymocytes proceeds in two separate steps. The major TCRloCD4+8+ subset appeared a dead end subset and showed no up-regulation of TCR expression at any time.

Phenotype analysis of cycling and postcycling thymocytes: evaluation of detection methods for BrdUrd and surface proteins

We present a comparison of two different methods for simultaneous detection of bromodeoxyuridine and cell surface markers. Both methods use enzymatic generation of single-strand DNA with nuclease. The biological system used is the murine thymus, in which in vivo DNA synthetizing cells were labeled by injection of BrdUrd and analyzed at different time points after the nucleoside pulse. The surface proteins detected were CD4 and CD8 differentiation markers and the T-cell receptor. Extraction of DNA-associated proteins with 0.1N HCl and detergent is necessary for the action of EcoR1 and Exonuclease III, but this treatment destroys phycocyanins and induces cell aggregation, as shown using the doublet-discrimination module. For DNAse I action, cells could be treated with paraformaldehyde and a low concentration of Tween 20, and this treatment was adequate for surface staining preservation (even with phycocyanins) and BrdUrd detection. Both methods were adequate for cell cycle studies, but only 7-amino-actinomycin D could be used as total DNA dye after DNAse action, and good results needed long (48-72 h) incubation in the fixative-detergent mixture. The DNAse I method now allows three-color staining (two surface markers and Brd-Urd), analyzed in a one laser-cytometer for the study of the phenotype of cycling cells, and of their progeny, in vivo and in cell cultures. It also allows the quantitative analysis of cell surface receptor densities in conditions similar to fresh cells.

A novel CD45RA+CD4+ transient thymic subpopulation in MRL-lpr/lpr mice: its relation to non-proliferating CD4-CD8-CD45RA+ tumor cells

MRL-lpr/lpr mice have hypertrophied lymph nodes comprising CD4-CD8- T cells. In addition, they contain CD4+CD8- T cells co-expressing the CD45RA marker. The correlation between these two subpopulations has been difficult to assess. We analyzed the expression of CD45RA (with the RA3-2C2 antibody) in various thymic and peripheral T cell subsets, using three-color immunofluorescence. We showed that in lpr mice (i) a transient CD4+CD8- thymic subset co-expresses CD45RA during the course of the disease, and (ii) thymic as well as peripheral CD4-CD8- and CD4+CD8- T cells brightly express CD45RA; furthermore (iii) in the lymph nodes, during lymphadenopathy, CD4+CD8-CD45RA+ T cells show a broad range of the CD4 fluorescence intensity, and (iv) the increase in MHC class II expression is restricted to CD45RA-T cells of the thymus and lymph nodes of lpr mice. Taken together, these data suggest that the CD4+CD8-CD45RA+ population might generate the CD4-CD8- tumor cells. In addition, using the bromodeoxyuridine labeling technique, we demonstrate that these cells are not the result of increased proliferation.

Thy-1 modulation and cell proliferation at early steps of intrathymic bone marrow cell differentiation

Intrathymic (IT) transfer of bone marrow (BM) precursor cells in sublethally irradiated hosts has been widely used to study T cell differentiation and maturation. In this report we have used double congenic mice Ly 5.1 Thy 1.1 (host) and Ly 5.2 Thy 1.2 (donor) and detected cycling Ly 5.2+ BM cells by in vivo bromodeoxyuridine incorporation, before induction of the Thy 1.2 antigen. Until Day 9 post-transfer, some donor type cells express a high level of Thy 1.2 together with macrophage and granulocyte markers. A few days later, a Thy 1.2low population transiently B220+ was detected. Thereafter, donor type cells expressed an intermediate Thy 1.2 brightness; this population then persisted and surpassed the other subsets. Our findings permitted to establish a relationship between cell cycle and Thy 1 fluorescence intensity according to the sequence: Thy 1low resting, Thy 1low cycling, Thy 1high cycling, Thy 1high resting. Moreover, we have shown that cells from the myeloïd and B lineages can, in vivo, transiently express the Thy 1 antigen, develop and differentiate within the thymus microenvironment.

Routine cytogenetic prenatal diagnosis using dynamic banding (RBG-GBG): a highly reproducible method for amniocytes, fetal cord blood, and chorionic villus investigations

Dynamic banding (RBG-GBG) using pulse 5-bromodeoxyuridine (5-BrdU) incorporation during part of the last S-phase before harvesting has been used in prenatal investigations. This method has already been routinely applied in 1344 cytogenetic investigations. GBG and RBG bandings produced almost identical patterns to classical G- and R-banding methods except for heterochromatic portions and some euchromatic segments. Nevertheless, these discordances may be somewhat helpful for cytogenetic diagnosis (i.e., X numerical abnormalities). The results showed particularly good contrast and staining; 5-BrdU incorporation did not prevent additional staining. Likewise, previous RBG or GBG disclosure allowed further chromosomal identification with C-banding or nucleolar organizer staining. Simplicity and reproducibility were very helpful in cases with a low mitotic index. 5-BrdU had no significant effect on in-vitro damage because only 0.31 percent of cells were affected; so, we believe that dynamic banding should be used more extensively in cytogenetic investigations. Moreover, the staining and contrast qualities were very suitable for automatic methods of analysis now in use: i.e., metaphase finding and computer-assisted karyogram creation.

Prenatal diagnosis of PIBIDS

In a well-documented PIBIDS family, two investigations of DNA excision repair showed a severe defect in lymphocytes from the index case (residual repair activities were 10.6-12.1 per cent). The values for the mother, father, and sister were within the normal range when compared with a healthy control. In the pregnant mother, a prenatal diagnosis of PIBIDS was made by measuring UV-induced unscheduled DNA synthesis in cultivated amniotic fluid cells. Results ranged between 12.5 and 26.1 per cent depending on the UV doses applied and were consistent with an affected fetus. The parents opted for a termination of pregnancy. Following a therapeutic abortion, fetal skin fibroblasts were tested and showed a severe DNA excision-repair defect of 9.2-13.5 per cent of residual activity.

Trisomy 16q23----qter arising from a maternal t(13;16)(p12;q23): case report and evidence of the reciprocal balanced maternal rearrangement by the Ag-NOR technique

We describe a female new-born with partial trisomy of the long arm of chromosome 16. The chromosome anomaly was the result of an unbalanced segregation of a maternal translocation t(13;16)(p12;q23). Dynamic (RBG, GBG) banding and the Ag-NOR technique ascertained the reciprocal balanced maternal translocation between the 16q23----qter and 13q12----pter segments because nucleolar organizers were present on the tip of long arms of the derivative 16 maternal chromosome. As monosomy 13p has little or no deleterious effect we consider our case as exhibiting the phenotype of trisomy 16q23----qter free from any monosomic feature. Clinical effects are of less consequence as compared with previously published cases of partial trisomy 16q.

Accumulation of bromodeoxyuridine-labeled cells in central and peripheral lymphoid organs: minimal estimates of production and turnover rates of mature lymphocytes

Daily lymphocyte production in both central and peripheral lymphoid organs was evaluated by associating in vivo incorporation of bromodeoxyuridine (BrdUrd) with cell surface labeling and multi-parameter flow analysis. At least 10% of mature T and B lymphocytes are generated every 24 h. The kinetic behavior of these cell populations differs, however, in that mature B cells are generated predominantly in the precursor compartments of the bone marrow, while most mature T cell generation occurs at the periphery. Therefore, peripheral expansion is the major mechanism of mature T cell production in the adult mouse. By following the accumulation of BrdUrd-labeled cells in peripheral lymphoid organs we found that the progeny of the daily lymphocyte production was sufficient to renew 30%-40% of all peripheral T and B cells every 48 h, demonstrating a high turnover rate of mature lymphocytes. We also examined the conditions of BrdUrd labeling of cycling cells in vivo. We found that while greater than 90% of bone marrow and thymus cells in S phase were labeled with a single injection of BrdUrd, in peripheral lymphoid compartments 70% of T and B cells in S failed to incorporate BrdUrd. Particular schedules of BrdUrd administration were required to overcome the low labeling efficiency of mature cells in vivo. Prolonged BrdUrd administration, however, had toxic effects on resident cells. The low labeling efficiency of BrdUrd incorporation by mature cells, as well as its potential toxicity during prolonged administration, may explain controversial results obtained by the different strategies used to study lymphocyte population dynamics.