Human fetal B-lymphopoiesis and acute lymphoblastic leukaemia: the impact of trisomy 21
<p><strong>Background:</strong> Children with Down Syndrome (DS), caused by an extra copy of chromosome 21 (trisomy 21, T21) are at increased risk of developing acute myeloid leukaemia (ML-DS) and B lineage acute lymphoblastic leukaemia (ALL). This points to specific effects of T21...
| Main Author: | |
|---|---|
| Other Authors: | |
| Format: | Thesis |
| Published: |
2019
|
| Subjects: |
| _version_ | 1811139219479855104 |
|---|---|
| author | O'Byrne, S |
| author2 | Roberts, I |
| author_facet | Roberts, I O'Byrne, S |
| author_sort | O'Byrne, S |
| collection | OXFORD |
| description | <p><strong>Background:</strong> Children with Down Syndrome (DS), caused by an extra copy of chromosome 21 (trisomy 21, T21) are at increased risk of developing acute myeloid leukaemia (ML-DS) and B lineage acute lymphoblastic leukaemia (ALL). This points to specific effects of T21 on haematopoietic stem and progenitor cell (HSPC) biology. In ML-DS, all cases originate in fetal cells and T21, together with a <em>GATA1</em> mutation is essential for disease progression. By contrast, in DS-ALL, where the most frequent molecular abnormalities affect JAK2 signalling and <em>CRLF2</em>, clinical signs of leukaemia develop after the first year of life and there is so far no direct evidence for a fetal origin. However, previous work from the Roberts lab showed that T21 causes perturbation of haematopoiesis in second trimester fetal liver (FL) and, as well as increased erythromegakaryopoiesis, B-lymphopoiesis was also severely impaired. Furthermore, FL HSC show a reduced ability to generate B cells in vitro despite increased HSC numbers. Preliminary data suggests that B-lymphopoiesis may also be reduced in T21 fetal bone marrow (BM). However, the extent of the perturbations in fetal lymphopoiesis in BM, their molecular basis and the link to DS-ALL remain unclear.</p>
<p><strong>Aim:</strong> The aim of this project was to investigate the cellular and molecular mechanisms responsible for perturbed fetal B-lymphoid development in T21 and how this may contribute to ALL by addressing the following questions: 1. What is the cellular hierarchy and molecular basis for B-lymphoid development in normal fetal BM? 2. What is the impact of T21 on fetal BM B progenitor development? 3. What is the impact of T21 on the transcriptome of ALL blasts?</p>
<p><strong>Results:</strong> 1. <em>Normal fetal B-lymphopoiesis</em>: Flow cytometry of FL and fetal BM showed that fetal BM is the main site of B-lymphopoiesis during the second trimester and that there are fetal specific lymphoid populations: Early Lymphoid Progenitors (ELP) and PreProB progenitors. Functional (<em>in vitro</em> cultures and <em>in vivo</em> xenografts) demonstrated that PreProB progenitors are the first committed B progenitor. Molecular analysis (RNA-sequencing, single cell RT-qPCR, ATAC-sequencing) placed PreProB progenitors downstream of ELP and upstream of ProB progenitors. PreProB progenitors are also especially proliferative and share immunophenotypic, molecular and IgH rearrangement patterns with infant ALL (iALL).</p>
<p>2. <em>Fetal B-lymphopoiesis in T21 fetal BM</em>: Although the frequency of immunophenotypic HSC was higher in T21 fetal BM and LMPP frequency was normal, ELP and PreProB progenitors were virtually absent, indicating an even more profound defect in B-lymphopoiesis than previously observed in FL. Functional analysis revealed decreased B-lymphoid potential from T21 HSC suggesting a cell intrinsic defect in Blymphopoiesis at the HSC level. RNA-Sequencing analysis of normal and T21 fetal BM HSPC showed enrichment for gene signatures associated with inflammatory pathways including IFNα signalling, suggesting a potential role for extrinsic, microenvironmentdriven factors. Novel co-cultures using normal fetal HSPC and normal or T21 fetal BM mesenchymal stromal cells (MSC) demonstrated that T21 MSC have reduced capacity to support fetal B-lymphopoiesis. Also, analysis of the MSC transcriptome pointed towards a role for inflammation in the perturbation in fetal B-lymphopoiesis.</p>
<p>3. <em>Transcriptomic analysis of cytogenetically matched paediatric non-DS-ALL and DS-ALL blasts</em>: Analysis of RNA-sequencing data from non-DS-ALL blasts, DS-ALL blasts and non-DS-ALL blasts with acquired T21 suggested that the ALL-associated cytogenetic abnormality was the main driver promoting clustering of samples by PCA. The impact of acquired T21 was distinct from that of constitutional T21, which also pointed towards a role for the trisomic microenvironment in DS-ALL because gene sets for inflammatory signalling pathways were enriched exclusively in DS-ALL blasts and HSC from DS-ALL patient BM. In addition, the increased frequency of immunophenotypic HSC observed in T21 fetal BM was found to persist in post-natal DS-ALL BM.</p>
<p><strong>Conclusions:</strong> Fetal specific B-lymphoid development pathways in human BM have been identified for the first time paving the way for further studies to identify and characterise in utero initiation of infant and paediatric ALL. In T21, fetal BM Blymphopoiesis is severely perturbed and specifically there appears to be a block in the normal fetal programme via ELP and PreProB progenitors. Studies of HSPC and MSC, the major cellular component of the microenvironment, indicate that both cell intrinsic and cell extrinsic mechanisms play a role, possibly through altered crosstalk between HSPC and their environment; and an increased inflammatory response that inhibits fetal B-lymphopoiesis. The inflammatory signature observed in T21 fetal life is also observed in DS-ALL and so together, these data indicate that perturbation of B-lymphopoiesis by T21 persists beyond the FL in the fetal BM and possibly in post-natal life</p> |
| first_indexed | 2024-03-07T05:49:48Z |
| format | Thesis |
| id | oxford-uuid:e87954e1-e298-42ad-b26f-e771e4e6beeb |
| institution | University of Oxford |
| last_indexed | 2024-09-25T04:02:37Z |
| publishDate | 2019 |
| record_format | dspace |
| spelling | oxford-uuid:e87954e1-e298-42ad-b26f-e771e4e6beeb2024-05-02T08:09:56ZHuman fetal B-lymphopoiesis and acute lymphoblastic leukaemia: the impact of trisomy 21Thesishttp://purl.org/coar/resource_type/c_db06uuid:e87954e1-e298-42ad-b26f-e771e4e6beebDown SyndromeLeukaemiaHaematologyORA Deposit2019O'Byrne, SRoberts, IRoy, A<p><strong>Background:</strong> Children with Down Syndrome (DS), caused by an extra copy of chromosome 21 (trisomy 21, T21) are at increased risk of developing acute myeloid leukaemia (ML-DS) and B lineage acute lymphoblastic leukaemia (ALL). This points to specific effects of T21 on haematopoietic stem and progenitor cell (HSPC) biology. In ML-DS, all cases originate in fetal cells and T21, together with a <em>GATA1</em> mutation is essential for disease progression. By contrast, in DS-ALL, where the most frequent molecular abnormalities affect JAK2 signalling and <em>CRLF2</em>, clinical signs of leukaemia develop after the first year of life and there is so far no direct evidence for a fetal origin. However, previous work from the Roberts lab showed that T21 causes perturbation of haematopoiesis in second trimester fetal liver (FL) and, as well as increased erythromegakaryopoiesis, B-lymphopoiesis was also severely impaired. Furthermore, FL HSC show a reduced ability to generate B cells in vitro despite increased HSC numbers. Preliminary data suggests that B-lymphopoiesis may also be reduced in T21 fetal bone marrow (BM). However, the extent of the perturbations in fetal lymphopoiesis in BM, their molecular basis and the link to DS-ALL remain unclear.</p> <p><strong>Aim:</strong> The aim of this project was to investigate the cellular and molecular mechanisms responsible for perturbed fetal B-lymphoid development in T21 and how this may contribute to ALL by addressing the following questions: 1. What is the cellular hierarchy and molecular basis for B-lymphoid development in normal fetal BM? 2. What is the impact of T21 on fetal BM B progenitor development? 3. What is the impact of T21 on the transcriptome of ALL blasts?</p> <p><strong>Results:</strong> 1. <em>Normal fetal B-lymphopoiesis</em>: Flow cytometry of FL and fetal BM showed that fetal BM is the main site of B-lymphopoiesis during the second trimester and that there are fetal specific lymphoid populations: Early Lymphoid Progenitors (ELP) and PreProB progenitors. Functional (<em>in vitro</em> cultures and <em>in vivo</em> xenografts) demonstrated that PreProB progenitors are the first committed B progenitor. Molecular analysis (RNA-sequencing, single cell RT-qPCR, ATAC-sequencing) placed PreProB progenitors downstream of ELP and upstream of ProB progenitors. PreProB progenitors are also especially proliferative and share immunophenotypic, molecular and IgH rearrangement patterns with infant ALL (iALL).</p> <p>2. <em>Fetal B-lymphopoiesis in T21 fetal BM</em>: Although the frequency of immunophenotypic HSC was higher in T21 fetal BM and LMPP frequency was normal, ELP and PreProB progenitors were virtually absent, indicating an even more profound defect in B-lymphopoiesis than previously observed in FL. Functional analysis revealed decreased B-lymphoid potential from T21 HSC suggesting a cell intrinsic defect in Blymphopoiesis at the HSC level. RNA-Sequencing analysis of normal and T21 fetal BM HSPC showed enrichment for gene signatures associated with inflammatory pathways including IFNα signalling, suggesting a potential role for extrinsic, microenvironmentdriven factors. Novel co-cultures using normal fetal HSPC and normal or T21 fetal BM mesenchymal stromal cells (MSC) demonstrated that T21 MSC have reduced capacity to support fetal B-lymphopoiesis. Also, analysis of the MSC transcriptome pointed towards a role for inflammation in the perturbation in fetal B-lymphopoiesis.</p> <p>3. <em>Transcriptomic analysis of cytogenetically matched paediatric non-DS-ALL and DS-ALL blasts</em>: Analysis of RNA-sequencing data from non-DS-ALL blasts, DS-ALL blasts and non-DS-ALL blasts with acquired T21 suggested that the ALL-associated cytogenetic abnormality was the main driver promoting clustering of samples by PCA. The impact of acquired T21 was distinct from that of constitutional T21, which also pointed towards a role for the trisomic microenvironment in DS-ALL because gene sets for inflammatory signalling pathways were enriched exclusively in DS-ALL blasts and HSC from DS-ALL patient BM. In addition, the increased frequency of immunophenotypic HSC observed in T21 fetal BM was found to persist in post-natal DS-ALL BM.</p> <p><strong>Conclusions:</strong> Fetal specific B-lymphoid development pathways in human BM have been identified for the first time paving the way for further studies to identify and characterise in utero initiation of infant and paediatric ALL. In T21, fetal BM Blymphopoiesis is severely perturbed and specifically there appears to be a block in the normal fetal programme via ELP and PreProB progenitors. Studies of HSPC and MSC, the major cellular component of the microenvironment, indicate that both cell intrinsic and cell extrinsic mechanisms play a role, possibly through altered crosstalk between HSPC and their environment; and an increased inflammatory response that inhibits fetal B-lymphopoiesis. The inflammatory signature observed in T21 fetal life is also observed in DS-ALL and so together, these data indicate that perturbation of B-lymphopoiesis by T21 persists beyond the FL in the fetal BM and possibly in post-natal life</p> |
| spellingShingle | Down Syndrome Leukaemia Haematology O'Byrne, S Human fetal B-lymphopoiesis and acute lymphoblastic leukaemia: the impact of trisomy 21 |
| title | Human fetal B-lymphopoiesis and acute lymphoblastic leukaemia: the impact of trisomy 21 |
| title_full | Human fetal B-lymphopoiesis and acute lymphoblastic leukaemia: the impact of trisomy 21 |
| title_fullStr | Human fetal B-lymphopoiesis and acute lymphoblastic leukaemia: the impact of trisomy 21 |
| title_full_unstemmed | Human fetal B-lymphopoiesis and acute lymphoblastic leukaemia: the impact of trisomy 21 |
| title_short | Human fetal B-lymphopoiesis and acute lymphoblastic leukaemia: the impact of trisomy 21 |
| title_sort | human fetal b lymphopoiesis and acute lymphoblastic leukaemia the impact of trisomy 21 |
| topic | Down Syndrome Leukaemia Haematology |
| work_keys_str_mv | AT obyrnes humanfetalblymphopoiesisandacutelymphoblasticleukaemiatheimpactoftrisomy21 |