CTG18.1 and ERDA-1 CAG/CTG repeat size in bipolar disorder

Several groups have reported association between large CAG/CTG repeat sequences in the genome and bipolar disorder using the Repeat Expansion Detection (RED) method. Unfortunately, the RED method cannot identify the specific repeat(s) responsible for these findings but it has recently been proposed that around 90% of the large CAG/CTG repeats detected by RED can be explained by repeat size at either CTG18.1, which maps to 18q21.1, or ERDA-1 (also known as Dir 1), which maps to 17q21.3. These data suggest that the previous associations between bipolar disorder and large CAG/CTG repeats might be explained at least in part by a specific association between bipolar disorder and either or both of these loci. However, using a case control study design, we find no evidence for such associations. Thus we conclude that in our sample, the previous RED associations are not a result of large CAG/CTG repeats at CTG18.1 or ERDA-1.

CAG repeat length in the hKCa3 gene and symptom dimensions in schizophrenia

BACKGROUND

Long CAG repeats in the hKCa3 potassium channel gene have been associated with schizophrenia. We sought evidence for associations between this polymorphism and aspects of the schizophrenia phenotype.

METHODS

Associations were investigated between CAG repeat length and gender, age of illness onset, and psychotic symptom dimensions in 203 unrelated individuals with DSM-IIIR schizophrenia.

RESULTS

No association was found between CAG repeat length and gender or age of onset. Long CAG repeats were associated with higher negative symptom dimension scores.

CONCLUSIONS

This study provides preliminary evidence that genetic liability to negative symptoms in schizophrenia may be partly mediated through the hKCa3 gene.

No association between a polymorphic CAG repeat in the human potassium channel gene hKCa3 and bipolar disorder

A recent case-control study suggested that modest enlargements of a CAG repeat in the hKCa3 potassium channel may be associated with bipolar disorder. We tried to replicate this result in a UK Caucasian sample of 203 DSM-IV bipolar I disorder patients and 206 controls group-matched for age and sex. Using the same model of analysis as the earlier study, bipolar probands did not have a higher frequency of alleles with greater than 19 repeats than controls (chi2 = 1.44, 1 df, P = 0.23). Similarly, comparison of the distributions of repeat sizes between probands and controls did not approach statistical significance (Mann-Whitney U test, P = 0.35). We conclude that our data provide no support for the hypothesis that variation at the hKCa3 gene contributes to susceptibility to bipolar disorder.

Eleven trinucleotide repeat loci that map to chromosome 12 excluded from involvement in the pathogenesis of bipolar disorder

The hypothesis that one or more genes containing expanded trinucleotide repeats contribute to the pathogenesis of bipolar disorder has received support from three independent studies demonstrating that bipolar patients tend to have larger CAG/CTG repeat expansion detection products than controls. In an attempt to identify the specific expanded CAG/CTG locus or loci which are associated with bipolar disorder, we determined repeat size at CAG/CTG loci mapping to candidate regions for bipolar disorder. Recent linkage studies suggest the existence of a bipolar susceptibility gene on chromosome 12q23-q24.1 in the region of the Darier's disease (DAR) gene. In this study we report our findings from 11 loci which map to chromosome 12, including CAG repeat polymorphisms within the genes SCA2 and ASH1. We conclude that all of these loci are excluded as candidates for CAG/CTG repeat expansion in bipolar disorder.

Accumulation of methotrexate polyglutamates, ploidy and trisomies of both chromosomes 4 and 10 in lymphoblasts from children with B-progenitor cell acute lymphoblastic leukemia: a Pediatric Oncology Group Study

Levels of accumulation of methotrexate polyglutamates were measured in vitro in lymphoblasts obtained at diagnosis from children with B-progenitor cell acute lymphoblastic leukemia (pro-B ALL). They were compared to numerical and structural chromosomal abnormalities present in these leukemic cells. In a series of 95 patients, the percent with high lymphoblast methotrexate polyglutamate levels increased with the increase in modal number of total chromosomes (p<0.001). Thus, lymphoblast methotrexate polyglutamate accumulation appeared to be closely linked to the extent of hyperdiploidy in childhood pro-B ALL. Lymphoblasts from 35 (88%) of the 40 children with hyperdiploid (>50 chromosomes) and 23 (88%) of 26 with hyperdiploid (DNA Index >1.16) pro-B ALL accumulated high levels of methotrexate polyglutamate, suggesting that they were more sensitive to methotrexate cytotoxicity. While children with hyperdiploid (DNA Index >1.16) pro-B ALL have a good prognosis, those with trisomies of both chromosomes 4 and 10, almost all of whom are hyperdiploid, have an even better outcome. There was no significant difference in methotrexate polyglutamate levels in lymphoblasts from 19 children with and 21 without trisomies of both chromosomes 4 and 10 (p = 0.25). The improved response to multi-agent chemotherapy conferred by the presence of trisomies of both chromosomes 4 and 10 in such patients may be due to increased sensitivity of their lymphoblasts to one or more anti-leukemic agents in addition to methotrexate.

T lymphocytes with a normal ADA gene accumulate after transplantation of transduced autologous umbilical cord blood CD34+ cells in ADA-deficient SCID neonates

Adenosine deaminase-deficient severe combined immunodeficiency was the first disease investigated for gene therapy because of a postulated production or survival advantage for gene-corrected T lymphocytes, which may overcome inefficient gene transfer. Four years after three newborns with this disease were given infusions of transduced autologous umbilical cord blood CD34+ cells, the frequency of gene-containing T lymphocytes has risen to 1-10%, whereas the frequencies of other hematopoietic and lymphoid cells containing the gene remain at 0.01-0.1%. Cessation of polyethylene glycol-conjugated adenosine deaminase enzyme replacement in one subject led to a decline in immune function, despite the persistence of gene-containing T lymphocytes. Thus, despite the long-term engraftment of transduced stem cells and selective accumulation of gene-containing T lymphocytes, improved gene transfer and expression will be needed to attain a therapeutic effect.

Association between functional psychosis and expanded CAG/CTG repeats is not explained by health stratification

A number of studies have reported an association between large CAG/CTG repeats and both schizophrenia and bipolar disorder. Recently, we reported an inverse correlation between CAG/CTG repeat size and age in a health-selected population, raising the possibility that selection of control groups for physical health was a confounding factor in our previous association studies. We investigated this by health-selection of patients with schizophrenia and bipolar disorder. The maximum CAG/CTG repeat size remained significantly larger in probands with functional psychosis compared with control individuals, and in probands with a diagnosis of schizophrenia compared with control individuals. The number of probands in the healthy bipolar group was small, and although on average this group also had longer CAG/CTG repeats than control individuals, this failed to reach statistical significance. Our findings do not support the notion that the original results with psychosis as a whole, and schizophrenia specifically, are attributable to a stratification effect consequent on health selection. Nevertheless, we are unable formally to reject the hypothesis that the previously observed difference between bipolar probands and control individuals is the result of this phenomenon.

Further support for an association between a polymorphic CAG repeat in the hKCa3 gene and schizophrenia

A recent study has suggested that a polymorphism in the hKCa3 potassium channel may be associated with raised susceptibility to schizophrenia. Despite its modest statistical significance, the study is intriguing for two reasons. First, hKCa3 contains a polymorphic CAG repeat in its coding sequence, with large repeats more common in schizophrenics compared with controls. This is interesting in view of several repeat expansion detection (RED) studies that have reported an excess of large CAG repeats in psychotic probands. Second, the hKCa3 gene is a functional candidate gene because studies of antipsychotic and psychotogenic compounds suggest that glutamatergic systems modulated by SKCa channels may be important in schizophrenia pathogenesis. In the light of the above, we have tested the hypothesis of an association between schizophrenia and the hKCa3 CAG repeat polymorphism using a case control study design. Under the same model of analysis as the earlier study, schizophrenic probands had a higher frequency of alleles with greater than 19 repeats than controls (chi 2 = 2.820, P = 0.047, 1-tail). Our data therefore provide modest support for the hypothesis that polymorphism in the hKCa3 gene may contribute to susceptibility to schizophrenia.

Translocations involving chromosome 12p11-13, methotrexate metabolism, and outcome in childhood B-progenitor cell acute lymphoblastic leukemia: a Pediatric Oncology Group study

Children with B-progenitor cell acute lymphoblastic leukemia whose lymphoblasts at diagnosis accumulate high levels of methotrexate (MTX) and MTX polyglutamates (MTXPGs) appear to have a good prognosis. This has been attributed to increased sensitivity of their blast cells to MTX. However, the proportion of children who are cured of B-progenitor cell acute lymphoblastic leukemia exceeds the number whose lymphoblasts accumulate high MTXPG levels. We report that lymphoblasts from patients with < 50 chromosomes who have translocations that involve the short arm of chromosome 12 accumulate low levels of MTXPGs. These patients appear to have an excellent survival because none of 14 patients with translocations affecting 12p has relapsed, 26-79 months following diagnosis.

Linked polymorphisms upstream of exons 1 and 2 of the human cholecystokinin gene are not associated with schizophrenia or bipolar disorder

The evidence for a significant genetic contribution to the functional psychoses (schizophrenia and bipolar disorder) is now well established. However, in both cases, the non-mendelian mode of inheritance has made the identification of susceptibility loci particularly challenging. The neuropeptide cholecystokinin (CCK) is present both in the gut and the CNS. Studies of CCK-like immunoreactivity and CCK mRNA levels in human brains have revealed high concentrations in numerous loci and shown colocalisation of CCK with, for example, dopamine and tyrosine hydroxylase. Furthermore, antagonists of CCK-B receptors, which are found most frequently in the brain, inhibit the activity of brain dopamine neurons. Such findings suggest that, with respect to neuropsychiatric disorders, CCK is a suitable candidate for analysis using methods to detect gene variations which have the potential to affect protein structure or expression. In the present study, mutation analyses were carried out on the human CCK gene. Linked polymorphisms were found in the promoter region and in intron 1 close to the 3' mRNA splice acceptor site. However, the allele frequencies of these polymorphisms in samples of individuals affected with either schizophrenia (n=117) or bipolar disorder (n=124) did not differ from those of control subjects (n=234), suggesting that these variations do not confer a predisposition to either of the functional psychoses.

Exclusion of expansion of 50 CAG/CTG trinucleotide repeats in bipolar disorder

OBJECTIVE

The purpose of this study was to identify the specific expanded CAG/CTG trinucleotide repeat associated with bipolar disorder.

METHOD

The study employed an efficient multistage approach for using a genomic CAG/CTG screening set.

RESULTS

The authors found no evidence of expanded repeats at 43 polymorphic autosomal loci and seven X chromosomal loci. Secondary screening was pursued at the only locus that contained a large allele (37 repeats) in the primary screening. No association was found between allele size and diagnostic status.

CONCLUSIONS

It is highly unlikely that expansions in repeat size at any of the 50 candidate trinucleotide repeat loci examined are responsible for the association between expanded CAG/ CTG repeats and bipolar disorder. However, although the authors prioritized the repeats that were a priori most likely to be involved, the study does not reject the more general hypothesis that expanded CAG/CTG repeats are implicated in the pathogenesis of bipolar disorder.

Exclusion of CAG/CTG trinucleotide repeat loci which map to chromosome 4 in bipolar disorder and schizophrenia

The hypothesis that expanded trinucleotide repeats contribute to the pathogenesis of schizophrenia and bipolar disorder has been recently supported by three independent studies which have shown that patients with either disorder tend to have larger CAG/CTG repeat expansion detection products than controls. In an attempt to identify the specific expanded CAG/CTG locus or loci which are associated with schizophrenia and bipolar disorder, we determined the repeat size at CAG/CTG loci mapping to candidate regions for psychosis. In this study we report our findings from eight loci which map to chromosome 4. We conclude that these loci are unlikely candidates for CAG/CTG repeat expansion in schizophrenia and bipolar disorder.

Undifferentiated rhabdomyosarcoma with lymphoid phenotype expression

Poorly differentiated rhabdomyosarcomas are traditionally distinguished from lymphomas by their absence of lymphoid markers such as immunoglobulin or CD20 expression. We have encountered three alveolar rhabdomyosarcomas that were initially diagnosed as lymphoid neoplasms because of the expression of a lymphocytic phenotype in morphologically undifferentiated tumor cells. Subsequent cytogenetic analysis revealed a t(2; 13) in two cases. All cases recurred in the chest wall and showed positivity for muscle markers, such as muscle-specific actin, myoglobin, MyoD1, and/or desmin on subsequent immunohistochemistry. The findings in these three cases lead us to conclude that the presence of a lymphoid phenotype does not absolutely exclude the diagnosis of rhabdomyosarcoma.

Confirmation of association between expanded CAG/CTG repeats and both schizophrenia and bipolar disorder

Recent studies have suggested that expanded CAG/CTG repeats contribute to the genetic aetiology of schizophrenia and bipolar disorder. However, the nature of this contribution is uncertain and difficult to predict from other known trinucleotide repeat diseases that display much simpler patterns of inheritance. We have sought to replicate and extend earlier findings using Repeat Expansion Detection in an enlarged sample of 152 patients with schizophrenia, 143 patients with bipolar disorder, and 160 controls. We have also examined DNA from the parents of 62 probands with schizophrenia or bipolar disorder. Our results confirm our earlier, preliminary findings of an association between expanded trinucleotide repeats and both schizophrenia and bipolar disorder. However, our data do not support the hypothesis that trinucleotide repeat expansion can alone explain the complex patterns of inheritance of the functional psychoses neither can this mechanism fully explain apparent anticipation.

Expansion of 50 CAG/CTG repeats excluded in schizophrenia by application of a highly efficient approach using repeat expansion detection and a PCR screening set

Studies of the transmission of schizophrenia in families with affected members in several generations have suggested that an expanded trinucleotide repeat mechanism may contribute to the genetic inheritance of this disorder. Using repeat expansion detection (RED), we and others have previously found that the distribution of CAG/CTG repeat size is larger in patients with schizophrenia than in controls. In an attempt to identify the specific expanded CAG/CTG locus or loci associated with schizophrenia, we have now used an approach based on a CAG/CTG PCR screening set combined with RED data. This has allowed us to minimize genotyping while excluding 43 polymorphic autosomal loci and 7 X-chromosomal loci from the screening set as candidates for expansion in schizophrenia with a very high degree of confidence.

Second allogeneic transplants for leukemia using blood instead of bone marrow as a source of hemopoietic cells

There is increasing interest in blood cell transplants (BCT) from normal donors as an alternative to BMT. Ten patients with relapsed or persistent leukemia after BMT received intensive cytotoxic conditioning followed by allogeneic BCT. Three BCT were from single-antigen mismatched donors; two of the corresponding recipients had rejected a BMT from the same donor. Two patients received BCT from a different donor (one matched, one single-antigen mismatched). The other six BCT were from the same, fully matched, bone marrow donors. Donors were given G-CSF to mobilize progenitor cells which were collected by a single 2-4 h leukapheresis. Methotrexate, CsA and folinic acid were used for GVHD prophylaxis for all transplants but CsA was discontinued sooner after BCT than after BMT. One patient died without engraftment having rejected a BMT from the same single-antigen mismatched donor 4 years previously. Nine patients had granulocyte recovery at a median of 14 days, up to 6 days faster than with their previous BMT. Platelet recovery was also 2-6 days faster than with BMT in four previously engrafting patients. Four patients died without platelet recovery after BCT within a year of BMT, three of treatment-related toxicity and one of relapse. Two patients developed grade II acute GVHD. Of six patients given BCT more than a year from BMT, four, all with acute leukemia, survive 7, 14, 29 and 29 months after BCT and one relapsed at 7 months. All four survivors developed chronic GVHD. These results indicate that BCT may be useful therapy for relapse occurring more than a year after BMT.

Outcome of unrelated donor bone marrow transplantation in 40 children with Hurler syndrome

Long-term survival and improved neuropsychological function have occurred in selected children with Hurler syndrome (MPS I H) after successful engraftment with genotypically matched sibling bone marrow transplantation (BMT). However, because few children have HLA-identical siblings, the feasibility of unrelated donor (URD) BMT as a vehicle for adoptive enzyme therapy was evaluated in this retrospective study. Forty consecutive children (median, 1.7 years; range, 0.9 to 3.2 years) with MPS I H received high-dose chemotherapy with or without radiation followed by BMT between January 27, 1989 and May 13, 1994. Twenty-five of the 40 patients initially engrafted. An estimated 49% of patients are alive at 2 years, 63% alloengrafted and 37% autoengrafted. The probability of grade II to IV acute graft-versus-host disease (GVHD) was 30%, and the probability of extensive chronic GVHD was 18%. Eleven patients received a second URD BMT because of graft rejection or failure. Of the 20 survivors, 13 children have complete donor engraftment, two children have mixed chimeric grafts, and five children have autologous marrow recovery. The BM cell dose was correlated with both donor engraftment and survival. Thirteen of 27 evaluable patients were engrafted at 1 year following URD BMT. Neither T-lymphocyte depletion (TLD) of the bone marrow nor irradiation appeared to influence the likelihood of engraftment. Ten of 16 patients alive at 1 year who received a BM cell dose greater than or equal to 3.5 x 10(8) cells/kg engrafted, and 62% are estimated to be alive at 3 years. In contrast, only 3 of 11 patients receiving less than 3.5 x 10(8) cells/kg engrafted, and 24% are estimated to be alive at 3 years (P = .05). The mental developmental index (MDI) was assessed before BMT. Both baseline and post-BMT neuropsychological data were available for 11 engrafted survivors. Eight children with a baseline MDI greater than 70 have undergone URD BMT (median age, 1.5 years; range, 1.0 to 2.4 years). Of these, two children have had BMT too recently for developmental follow-up. Of the remaining six, none has shown any decline in age equivalent scores. Four children are acquiring skills at a pace equal to or slightly below their same age peers; two children have shown a plateau in learning or extreme slowing in their learning process. For children with a baseline MDI less than 70 (median age, 2.5 years; range, 0.9 to 2.9 years), post-BMT follow-up indicated that two children have shown deterioration in their developmental skills. The remaining three children are maintaining their skills and are adding to them at a highly variable rate. We conclude that MPS I H patients with a baseline MDI greater than 70 who are engrafted survivors following URD BMT can achieve a favorable long-term outcome and improved cognitive function. Future protocols must address the high risk of graft rejection or failure and the impact of GVHD in this patient population.

Allogeneic blood cell transplants for haematological malignancy: preliminary comparison of outcomes with bone marrow transplantation

Twenty-six patients with haematological malignancy received cryopreserved but otherwise unmanipulated blood cell transplants (BCT) from five- or six-antigen matched siblings in whom progenitor cells had been mobilized by G-CSF. Outcomes were compared with a historical control group of 26 BMT patients matched for age and disease status. Granulocyte counts recovered to 0.5 x 10(9)/l in a median of 16 days after BCT compared with 21.5 days after BMT (P = 0.0002). Platelet counts, unsupported for 3 days, reached 20 x 10(9)/l in a median of 14 days vs 20.5 days (P = 0.0003) after BCT compared with BMT in those patients who engrafted. In the BCT and BMT groups, respectively, the risk of grade II-IV acute GVHD was 37 vs 21% (P = 0.16) and of chronic GVHD at 1 year 53 vs 48% (P = 0.9). There was no significant difference in red cell transfusions but BCT patients required fewer platelet transfusions (median 3 vs 5, P = 0.015) and fewer days in hospital (20.5 vs 25, P = 0.02). These results indicate that allogeneic BCT from matched and partially mismatched family donors result in faster engraftment than BMT without a significant increase in GVHD. Allogeneic BCT may prove to be a more tolerable procedure than BMT for both donor and recipient and there are indications of improved cost-effectiveness.

Enoxaparin for unstable angina and ancrod for cardiac surgery following heparin allergy

OBJECTIVE

To describe a patient who presented with heparin allergy and required alternate anticoagulation for unstable angina and coronary artery bypass surgery. To review therapeutic alternatives to porcine heparin for patients with hypersensitivity or intolerance to standard heparin anticoagulation.

CASE SUMMARY

A 74-year-old man with a 15-year-old coronary artery bypass graft presented to the emergency room with unstable angina and was scheduled for urgent coronary artery revascularization. A bolus dose of porcine heparin was administered followed by a continuous infusion. Shortly afterward the patient developed a type I allergic reaction to the porcine heparin that was confirmed by rechallenge. Three alternatives to porcine heparin were tried, including bovine lung heparin, low-molecular-weight heparin (enoxaparin), and ancrod. The patient was found to be cross-sensitive to bovine lung heparin, but tolerated enoxaparin for unstable angina without cross-sensitivity. Anticoagulation for cardiopulmonary bypass was achieved with an infusion of ancrod that was later reversed with cryoprecipitate. The patient was discharged postoperatively on day 5 without the complication of excessive bleeding.

DISCUSSION

Type I allergic reaction to unfractionated heparin is a rare occurrence and could be the result of a variety of factors. Possible causes for the reaction include a porcine protein, a preservative contained in the heparin solution, or a hapten formed between heparin and a plasma protein. We considered four alternatives to heparin anticoagulation: rush desensitization, bovine lung heparin, low-molecular-weight heparin, and ancrod. The patient was cross-sensitive to bovine lung heparin, but was able to tolerate low-molecular-weight heparin (enoxaparin). This was unexpected because enoxaparin is derived from unfractionated porcine heparin. Testing for cross-sensitivity had no value in this case, as two negative subcutaneous test doses were followed by dramatic reactions when the drugs were given intravenously. Although enoxaparin has been used for anticoagulation during bypass surgery, there is more experience with ancrod as an alternative to heparin. Repeat bypass surgery, which normally results in above-average blood loss, was successfully performed with a very low fibrinogen concentration (< 0.15 g/L) during ancrod anticoagulation.

CONCLUSIONS

We conclude that ancrod was a safe and effective alternative to heparin for coronary artery bypass surgery in this patient in whom a heparin product had caused a hypersensitivity reaction. We discovered on two occasions that a negative subcutaneous test dose for heparin allergy did not predict a severe type I allergic reaction when the heparin was later administered intravenously. Furthermore, we found that a low-molecular-weight heparin administered subcutaneously for a short period of time did not cause cross-sensitivity in a patient with a type I allergy to unfractionated heparin.

High-dose melphalan and cyclophosphamide with autologous bone marrow rescue for recurrent/progressive malignant brain tumors in children: a pilot pediatric oncology group study

PURPOSE

To determine the maximum-tolerated dose of cyclophosphamide (CTX) when administered sequentially with melphalan 60 mg/m2/d for 3 days, followed by autologous bone marrow rescue (ABMR), in children with recurrent or progressive malignant brain tumors, and to make preliminary observations on efficacy.

PATIENTS AND METHODS

Nineteen patients between the ages of 2 and 21 years were enrolled and 18 were assessable for effects of therapy. CTX was administered to seven patients at 750 mg/m2/d for 4 days, to five patients at 975 mg/m2/d, to three patients at 1,200 mg/m2/d, and to three patients at 1,500 mg/m2/d. All patients received ABMR. Granulocyte-macrophage colony-stimulating factor (GM-CSF) was used in 15 patients. Toxicity, response to therapy, time to progression, and survival and monitored.

RESULTS

The median time to a granulocyte count more than 500/dL was 19 days (range, 11 to 39), and for a platelet count more than 50,000/dL was 33 days (range, 16 to 60). Four heavily pretreated patients (22%) died of transplant-related complications. No dose-limiting, non-hematologic toxicities were defined for the study. Seven of 18 patients (39%) had a complete response (CR) or a partial response (PR). These included four patients with medulloblastoma (CR and three PRs), two with germinomas (two CRs), and one with ependymoma (one CR). The estimated 1-year survival rate was 39% (SE 12%).

CONCLUSION

CTX, at a maximum total dose of 6,000 mg/m2, administered sequentially with melphalan and followed by ABMR was tolerable in children with recurrent brain tumors who had not been heavily pretreated. Responses were seen in patients with medulloblastoma and germinomas. Further trials in children with chemosensitive tumors, with minimal residual disease, are planned.

Three new adenosine deaminase mutations that define a splicing enhancer and cause severe and partial phenotypes: implications for evolution of a CpG hotspot and expression of a transduced ADA cDNA

We report three novel adenosine deaminase (ADA) mutations with interesting implications. A Somali child with severe combined immunodeficiency disease (SCID) had reduced ADA mRNA in T cells and was homozygous for the nonsense mutation Q3X. Unexpectedly, her healthy father was a compound ADA heterozygote whose second allele carried a 'partial' mutation, R142Q, due to a G-->A transition of a CpG dinucleotide. A C-->T transition of the same CpG produced a nonsense mutation, R142X, in two homozygous Canadian Mennonite infants with SCID. The severe and healthy phenotypes associated with R142X and R142Q, the high frequency of 'partial' ADA mutations arising from CpGs in healthy individuals of African descent and the presence of CAA (glutamine) at codon 142 in murine ADA, suggest selection for replacement of this CpG hotspot by CpA during ADA evolution. R142X, located within a purine-rich segment at nt 62/116 of exon 5, caused skipping of the exon, possibly by disrupting a splicing enhancer. Absence of exon 5 in T cell ADA mRNA and low ADA activity in T cells and erythrocytes obtained at age 18-22 months from one of the Mennonite children, indicate limited expression of a normal ADA cDNA from retrovirally transduced CD34+ umbilical cord leukocytes infused shortly after birth in an attempt at stem cell gene therapy.

PCR amplification of intergenic spacers in the ribosomal DNA of Drosophila melanogaster reveals high levels of turnover in length and copy-number of spacers in geographically separated populations

A recently described PCR-based method for the analysis of intergenic spacer (IGS) length variation in the ribosomal (r) DNA of Drosophila melanogaster was used to analyse the distribution of IGS length variants in the rDNA of a number of recently collected D. melanogaster populations. One group of populations, from Europe and North Africa, was shown to have low intrapopulation IGS length variation following maintenance of massed populations in the laboratory for an extended period. However, a greater degree of IGS profile variability was detected at a number of levels in the majority of laboratory-maintained isofemale lines from two of these populations plus a second group of populations which were collected more recently from the eastern coast of Australia; all of which were immediately divided into isofemale lines following collection. Interestingly, PCR analysis of pooled DNA extracts from 30 individuals of either sex showed almost identical PCR profiles from each of the Australian populations. These preliminary results are discussed with regard to the possible combinations of forces (natural selection, neutral drift and genomic molecular drive) on the patterns of IGS length variation.

The P1 blood group and the severity of diarrhea-associated hemolytic uremic syndrome

Thirty-one children with diarrhea-associated hemolytic uremic syndrome were retrospectively studied to determine if expression of the P1 blood type was related to the severity of the acute illness or to the prognosis. No differences were found in the clinical variables studied in the patients who were P1 positive compared to the patients who were P1 negative. The clinical variables studied included the age, hemoglobin, white blood cell count (WBC), and presence of central nervous system involvement at presentation, the duration of elevated WBC, thrombocytopenia, hemorrhagic colitis, and anuria, and the follow-up incidence of proteinuria, hypertension and decreased GFR. Expression of the P1 phenotype does not appear to exert a protective influence in patients with D+ HUS.