Scott Langdon

T Cell Repertoire Development in Humans with SCID After Nonablative Allogeneic Marrow Transplantation

Transplantation of HLA-identical or haploidentical T cell-depleted allogeneic bone marrow (BM) into SCID infants results in thymus-dependent T cell development in the recipients. Immunoscope analysis of the TCR Vβ repertoire was performed on 15 SCID patients given BM transplants. Before and within the first 100 days after bone marrow transplantation (BMT), patients’ PBMC displayed an oligoclonal or skewed T cell repertoire, low TCR excision circles (TREC) values, and a predominance of CD45RO+ T cells. In contrast, the presence of high numbers of CD45RA+ cells in the circulation of SCID patients >100 days post-BMT correlated with active T cell output by the thymus as revealed by high TREC values and a polyclonal T cell repertoire demonstrated by a Gaussian distribution of Vβ-specific peaks. Ten years after BMT, we observed a decrease of the normal polyclonal T cell repertoire and an increase of a more skewed T cell repertoire. A decline of TREC levels and a decrease in the number of CD45RA+ cells beyond 10 years after BMT was concomitant with the detection of oligoclonal CD3+CD8+CD45RO+ cells. The switch from a polyclonal to a more skewed repertoire, observed in the CD3+CD8+CD45RO+ T cell subset, is a phenomenon that occurs normally with decreased thymic output during aging, but not as rapidly as in this patient population. We conclude that a normal T cell repertoire develops in SCID patients as a result of thymic output and the repertoire remains highly diverse for the first 10 years after BMT. The TCR diversity positively correlates in these patients with TREC levels.

Genotype–phenotype correlation in MYH9‐related thrombocytopenia

Mutation of the non‐muscle myosin heavy chain type II‐A results in MYH9‐related hereditary macrothrombocytopenia (HMTC), including four autosomal dominant platelet disorders: May‐Hegglin anomaly (MHA), Sebastian (SBS), Fechtner (FS) and Epstein (EPS) syndrome. Denaturing high‐performance liquid chromatography (DHPLC) was optimised for rapid screening of the seven exons harbouring all but one of the previously reported mutations of MYH9. Individuals from 13 families with phenotypes suggestive of MYH9‐related HMTC were screened for mutations by DHPLC followed by direct sequencing of samples with aberrant column retention time. Mutations were identified in all 13 families. Six distinct missense heterozygous mutations were found in 10 families, including six families with MHA or SBS (E1841K, D1424N), three families with FS (R702H, R1165C, and D1424Y), and one family with EPS (S96L). A truncating mutation (R1933X) was found in three MHA families. A review of all published mutations suggests that mutation in the C‐terminal coiled coil region or truncation of the tailpiece is associated with haematological‐only phenotype, while mutation of the head ATPase domain frequently is associated with nephropathy and/or hearing loss. Mutations of other regions have intermediate expression of non‐haematological characteristics. Further study is required to confirm these associations and understand the molecular basis for this genotype–phenotype relationship.

Structural organization of the human MS4A gene cluster on Chromosome 11q12

CD20, the high-affinity IgE receptor β chain (FcεRIβ), and HTm4 are structurally related cell surface proteins expressed by hematopoietic cells. Recently, 16 novel human and mouse genes were identified that encode new members of this nascent protein family that we have named the membrane-spanning 4A gene family, with at least 12 subgroups (MS4A1–MS4A12). In the current study, we identified three additional human MS4A genes: MS4A4E, MS4A6E, and MS4A10. All family members have at least four potential transmembrane domains and N- and C-terminal cytoplasmic domains encoded by distinct exons, except MS4A6E which contains two transmembrane domains. Otherwise, the 12 currently identified MS4A genes share common structural features and similar intron/exon splice boundaries, and are clustered along an ~600-kb region of Chromosome 11q12. In contrast to other MS4A genes, MS4A4E, MS4A6E, and MS4A10 transcripts were rare and not detected among hematopoietic cells and most nonlymphoid tissues. Sequence polymorphisms were identified in the MS4A6E gene and common splice variants were observed for the MS4A4A, MS4A5, MS4A6A, and MS4A7 genes. Thus, the MS4A family currently includes 24 distinct human and mouse genes. Like CD20 and FcεRIβ, the 10 other human MS4A family members are likely to be components of oligomeric cell surface complexes involved in signal transduction in diverse cell lineages.

Interaction between transcriptional activator protein LAC9 and negative regulatory protein GAL80.

In Saccharomyces cerevisiae, transcriptional activation mediated by the GAL4 regulatory protein is repressed in the absence of galactose by the binding of the GAL80 protein, an interaction that requires the carboxy-terminal 28 amino acids of GAL4. The homolog of GAL4 from Kluyveromyces lactis, LAC9, activates transcription in S. cerevisiae and is highly similar to GAL4 in its carboxyl terminus but is not repressed by wild-type levels of GAL80 protein. Here we show that GAL80 does repress LAC9-activated transcription in S. cerevisiae if overproduced. We sought to determine the molecular basis for the difference in the responses of the LAC9 and GAL4 proteins to GAL80. Our results indicate that this difference is due primarily to the fact that under wild-type conditions, the level of LAC9 protein in S. cerevisiae is much higher than that of GAL4, which suggests that LAC9 escapes GAL80-mediated repression by titration of GAL80 protein in vivo. The difference in response to GAL80 is not due to amino acid sequence differences between the LAC9 and GAL4 carboxyl termini. We discuss the implications of these results for the mechanism of galactose metabolism regulation in S. cerevisiae and K. lactis.

A Polymorphism Within the Promoter of the TGFβ1 Gene Is Associated With Radiation Sensitivity Using an Objective Radiologic Endpoint

PURPOSE To evaluate whether single nucleotide polymorphisms (SNPs) in the transforming growth factor-β1 (TGFβ1) gene are associated with radiation sensitivity using an objective radiologic endpoint. METHODS AND MATERIALS Preradiation therapy and serial postradiation therapy single photon emission computed tomography (SPECT) lung perfusion scans were obtained in patients undergoing treatment for lung cancer. Serial blood samples were obtained to measure circulating levels of TGFβ1. Changes in regional perfusion were related to regional radiation dose yielding a patient-specific dose-response curve, reflecting the patients inherent sensitivity to radiation therapy. Six TGFβ1 SNPs (-988, -800, -509, 869, 941, and 1655) were assessed using high-resolution melting assays and DNA sequencing. The association between genotype and slope of the dose-response curve, and genotype and TGFβ1 ratio (4-week/preradiation therapy), was analyzed using the Kruskal-Wallis test. RESULTS 39 white patients with preradiation therapy and ≥ 6-month postradiation therapy SPECT scans and blood samples were identified. Increasing slope of the dose-response curve was associated with the C(-509)T SNP (p = 0.035), but not the other analyzed SNPs. This SNP was also associated with higher TGFβ1 ratios. CONCLUSIONS This study suggests that a polymorphism within the promoter of the TGFβ1 gene is associated with increased radiation sensitivity (defined objectively by dose-dependent changes in SPECT lung perfusion).

Analysis of Single Nucleotide Polymorphisms and Radiation Sensitivity of the Lung Assessed With an Objective Radiologic Endpoin

BACKGROUND The primary objective of this study was to evaluate the association between radiation sensitivity of the lungs and candidate single nucleotide polymorphisms (SNP) in genes implicated in radiation-induced toxicity. METHODS Patients with lung cancer who received radiation therapy (RT) had pre-RT and serial post-RT single photon emission computed tomography (SPECT) lung perfusion scans. RT-induced changes in regional perfusion were related to regional dose, which generated patient-specific dose-response curves (DRC). The slope of the DRC is independent of total dose and the irradiated volume, and is taken as a reflection of the patients inherent sensitivity to RT. DNA was extracted from blood samples obtained at baseline. SNPs were determined by using a combination of high-resolution melting, TaqMan assays, and direct sequencing. Genotypes from 33 SNPs in 22 genes were compared against the slope of the DRC by using the Kruskal-Wallis test for ordered alternatives. RESULTS Thirty-nine self-reported Caucasian patients with pre-RT and ≥6 month post-RT SPECTs, and blood samples were identified. An association between genotype and increasing slope of the DRC was noted in G(1301) A in XRCC1 (rs25487) (P = .01) and G(3748) A in BRCA1 (rs16942) (P = .03). CONCLUSIONS By using an objective radiologic assessment, polymorphisms within genes involved in repair of DNA damage (XRCC1 and BRCA1) were associated with radiation sensitivity of the lungs.