Genotypic analysis using a Y-chromosome-specific probe following bone marrow transplantation

Using quantitative real-time PCR to determine donor cell engraftment in a competitive murine bone marrow transplantation model

Murine bone marrow transplantation models provide an important tool in measuring hematopoietic stem cell (HSC) functions and determining genes/molecules that regulate HSCs. In these transplant model systems, the function of HSCs is determined by the ability of these cells to engraft and reconstitute lethally irradiated recipient mice. Commonly, the donor cell contribution/engraftment is measured by antibodies to donor- specific cell surface proteins using flow cytometry. However, this method heavily depends on the specificity and the ability of the cell surface marker to differentiate donor-derived cells from recipient-originated cells, which may not be available for all mouse strains. Considering the various backgrounds of genetically modified mouse strains in the market, this cell surface/ flow cytometry-based method has significant limitations especially in mouse strains that lack well-defined surface markers to separate donor cells from congenic recipient cells. Here, we reported a PCR-based technique to determine donor cell engraftment/contribution in transplant recipient mice. We transplanted male donor bone marrow HSCs to lethally irradiated congenic female mice. Peripheral blood samples were collected at different time points post transplantation. Bone marrow samples were obtained at the end of the experiments. Genomic DNA was isolated and the Y chromosome specific gene, Zfy1, was amplified using quantitative Real time PCR. The engraftment of male donor-derived cells in the female recipient mice was calculated against standard curve with known percentage of male vs. female DNAs. Bcl2 was used as a reference gene to normalize the total DNA amount. Our data suggested that this approach reliably determines donor cell engraftment and provides a useful, yet simple method in measuring hematopoietic cell reconstitution in murine bone marrow transplantation models. Our method can be routinely performed in most laboratories because no costly equipment such as flow cytometry is required.

Sex identification of normal persons and sex reverse cases from bloodstains using FISH and PCR

Sex identification of dry blood is of crucial importance in forensic medicine.

SUBJECTS AND METHODS

Sixty normal (with matching phenotypic and genotypic sex) persons (36 males and 24 females), and 7 cases of sex reverse, i.e., persons with one genotypic sex and ambiguous or external genitalia of the opposite sex (3 phenotypic females with Swyer syndrome and the 46,XY karyotype, and 4 phenotypic Klinefelter-like males with the 46,XX karyotype) were subjected to sex identification by FISH and PCR using bloodstains.

RESULTS

The FISH technique using an X/Y cocktail probe (DXZI & DYZI, Oncor) has identified the sex correctly in 91.69% of interphase nuclei of the 36 males of the study, and in 92.29% of cells of the 24 females and incorrectly identified the 3 phenotypic females with Swyer syndrome as males and the 4 Klinefelter-like males as females. The 60 normal individuals in the study were correctly typed to their phenotypic sex by the 2 PCR methods used, i.e., the single PCR using the amelogenin sequence specific for the X and Y chromosomes and the multiplex PCR using SRY gene (male-specific) and the AR gene (X-specific). Out of the 7 sex reverse cases, one Klinefelter-like male was incorrectly identified by PCR as female due to the absence of amplification of the SRY gene and the amelogenin male-specific 788 bp fragment.

CONCLUSION

The present study demonstrates that both FISH and PCR techniques are fast, easy to perform, reliable and efficient for sex identification but PCR is more accurate. It also emphasises that the sex identified is the genotypic sex which does not necessarily correspond to the phenotypic one and if evidences at the scene of crime indicate opposite sex of the accused, persons with sex reverse have to be ruled out using different X- and Y-specific probes and PCR.

Nonmyeloablative stem cell transplantation with fludarabine and cyclophosphamide for patients with hematologic malignancies

We conducted a multi-center phase I/II trial of nonmyeloablative stem cell transplantation for patients with hematologic malignancies. The aim of this trial was to assess the safety and feasibility of this treatment modality for older or younger patients with significant organ dysfunction, who could not be treated with conventional high dose chemoradiotherapy. Twelve patients were treated with a conditioning regimen consisting of fludarabine and cyclophosphamide, followed by peripheral blood stem cell transplantation from human leukocyte antigen (HLA) identical siblings. Nonhematologic toxicities were mild. Median time to absolute neutrophils above 0.5 x 10(9)/l, 1.0 x 10(9)/l and platelets above 50 x 10(9)/l were 8, 10 and 12 days, respectively. Donor dominant hematopoiesis was achieved in all patients, with or without donor leukocyte infusion. The cumulative incidence of acute and chronic graft-versus-host disease (GVHD) was 75 and 56%, respectively. Only one patient experienced early death within 100 days, caused by acute GVHD complicated by fungal infection. All patients except one achieved complete remission. With a median follow-up of 330 days, expected progression-free survival is 75%. Overall survival is 76%. Our study confirms that nonmyeloablative stem cell transplantation with cyclophosphamide and fludarabine conditioning is a safe and promising treatment for elderly patients with hematologic malignancies. A further study in large-scale setting is warranted.

Combined immunophenotyping and FISH with sex chromosome-specific DNA probes for the detection of chimerism in epidermal Langerhans cells after sex-mismatched bone marrow transplantation

Langerhans cells (LC) of the skin represent bone marrow-derived dendritic antigen-presenting cells and are therefore important in pathophysiological processes such as rejection, graft-versus-host disease, and graft-versus-leukemia-reaction after bone marrow transplantation (BMT). For understanding of these diseases, the evaluation of the chimeric status of LC following BMT is of great interest. To analyze the sex chromosome constitution of LC in the skin, we established a modified and refined technique of combined immunophenotyping and fluorescence in situ hybridization (FISH) and investigated frozen sections of skin biopsies from nine patients after allogeneic sex-mismatched BMT and of two healthy donors for control. LC were specifically labeled using a fluorescent CD1 a antibody and hybridized simultaneously with X and Y chromosome-specific DNA probes. The results of this practical application on nine leukemia patients show the appearance of donor-type LC and the persistence of host-type LC at various times (36 up to 1395 days) after sex-mismatched BMT. Complete chimerism of LC could not be detected in any case. The frequency of recipient-specific LC ranged from 7% to 92% and showed no correlation with time postgrafting. We conclude from our results of 1461 analyzed LC that combined immunophenotyping and interphase cytogenetic analysis by FISH is the method of choice for the assessment of chimerism in a particular cell type after sex-mismatched BMT. Its practical application on other tissues affected by BMT-related pathophysiological processes reveals further knowledge of the time-dependent course of chimeric patterns after BMT.

Assessment of graft status following allogeneic bone marrow transplantation for haematological disorders in children using locus-specific minisatellite probes

We have examined peripheral blood or bone marrow DNA following allogeneic bone marrow transplantation (BMT) in children suffering from a variety of haematological disorders. Using either locus-specific minisatellite probes separately or in combination with a Y specific probe for sex-mismatched transplants, complete haematological chimaerism, autologous reconstitution, or mixed chimaeric states have been defined immediately post-BMT. We have also been able to identify emerging autologous cells or relapse prior to morphological diagnosis. Forty-two children, mean age 6.4 years (range 9 months to 15 years), received an allogeneic BMT for: acute lymphoblastic leukaemia (ALL), n = 17; acute myeloid leukaemia (AML), n = 5; biphenotypic leukaemia, n = 1; myelodysplastic syndrome (MDS), n = 5; chronic granulocytic leukaemia (CGL), n = 1; severe aplastic anaemia (SAA), n = 7; familial erythrophagocytic lymphohistiocytosis (FEL), n = 2; beta thalassaemia major (beta thal), n = 1; and juvenile chronic myeloid leukaemia (JCML), n = 3. Immediately post-transplant, 78% had achieved complete haematological chimaerism, 12% had failed to engraft (DNA analysis confirmed autologous reconstitution) and 10% had mixed chimaerism. SAA was the underlying disease in two of the chimaeric cases, the third case having had a matched unrelated donor (MUD) BMT for MDS. In 3/4 cases which subsequently relapsed, DNA analysis showed re-emergence of autologous cells (indicative of relapse), prior to their morphological identification. We conclude that DNA analysis using minisatellite probes to assess graft status provides a useful contribution to patient management following allogeneic BMT.

Origin of hematopoietic progenitor cells after bone marrow transplantation: analysis by means of a Y-chromosome specific DNA probe

To characterize hematopoietic cells in mixed hematopoietic chimeras after allogeneic bone marrow transplantation (BMT), the authors examined the origin of progenies derived from hematopoietic progenitor cells of male recipients who received a marrow graft from female donors, by use of a Y-chromosome specific DNA (YDNA) probe in combination with an in vitro colony assay. Host-type hematopoietic cells were detected in cultured bone marrow mononuclear cells (BMMC) from 4 out of 6 patients studied, who were all in complete remission. In 2 patients of the mixed chimeras, the relative amount of host-derived YDNA from BMMC increased after methylcellulose cultures for 14 days. Analysis of individual colonies derived from granulocyte-macrophage colony forming units (CFU-GM) from these mixed chimeras, including 2 patients with chronic myelogenous leukemia (CML), revealed approximately 30% of total colonies were host-type, although no evidence for the existence of residual Ph1 positive cells was obtained by using polymerase chain reaction for detecting bcr-abl chimeric messenger RNA in the 2 CML patients. These findings provide direct evidence that considerable numbers of host-derived normal hematopoietic progenitors survive and persist for a long term in a certain population of marrow recipients, after BMT following supralethal radiochemotherapy.

Sex identification by polymerase chain reaction using X-Y homologous primer

A method of sex identification using the polymerase chain reaction technique is described. Using a pair of nucleotide primers from an X-Y homologous region, both the X and the Y sequences can be amplified simultaneously, and more importantly, they result in fragments of different lengths. The success of the procedure is therefore monitored by the presence of a X-specific band while sex is identified by the presence or absence of a Y-specific band.

Sex identification of forensic specimens by polymerase chain reaction (PCR): two alternative methods

Sex identification of forensic samples (bloodstains and decomposed tissue) by polymerase chain reaction (PCR) was investigated. Amplification of a segment of the amelogenin gene using a pair of primers revealed both Y- and X-specific bands at the same time. The gene has counterparts in both the X and Y chromosomes and a small deletion in the former made it possible to distinguish them. Analysis of the X-specific band is the most reliable method for sex identification. THe locus includes a single copy gene so a sample of 250 ng/tube of deoxyribonucleic acid (DNA) is required for identification. Amplification of part of the DYZ1 locus was attempted as an alternative method for analysis of infinitesimal amounts of sample. Even DNA from putrefied tissue could be analyzed by PCR because the locus consists of thousands of copies of repeating units pHY10.

Detection of engraftment and chimerism after bone marrow transplantation by in situ hybridization using a Y-chromosome specific probe

After bone marrow transplantation (BMT), the recipient and donor cells must be distinguished from each other to document and characterize successful engraftment. In addition to dot blot and Southern blot analyses, we have performed in situ hybridization in two sex-mismatched cases using a Y-chromosome specific DNA probe (PHY10). In situ hybridization showed that greater than 95% of the peripheral mononuclear cells had clusters of grains indicative of male cell origin in a recipient girl (case 1), and no cells had clusters of grains in another recipient boy (case 2) at the time of engraftment and 3 months after BMT. In situ hybridization using the PHY10 probe appears to facilitate identification of individual cells of male and female origin, and it requires only 20 hr to obtain the results. The technique provides a powerful new method for the documentation of engraftment and the detection of mixed hematopoietic chimerism in peripheral blood and bone marrow cell compartments after BMT.

Very low rate Y-chromosome mosaicism (1:5,400) detectable by a novel probe enzyme combination

DYZ1 is a repetitive DNA family located on the long arm of the Y chromosome and is the major component of the Q-positive region. DYZ1 consists of about 3,000 copies of a 3.4 kb repeat unit which mainly consists of a tandem array of pentanucleotides, TTCCA. Because of this large number of repeats, DYZ1 has been used as a probe in Southern hybridization for sensitive and rapid detection of the Y chromosome. In cases of XX/XY mosaicism, however, autosomal sequences having homology to DYZ1 hinder the detection of the Y chromosome, especially when the ratio of the Y-bearing cells is low. To solve this problem and improve the detection limit, we have sought the optimum hybridization condition by changing several variables. These variables include the length of probes, the methods of probe labeling, the endonucleases used to digest the genomic DNA and the hybridization buffer. Here we show that the StuI digestion of genomic DNA in combination with the nick translated DYZ1 probe significantly improves the detection limit of the Y-chromosome bearing cells. The presence of Y-chromosome bearing cells was detectable against a background of 5,400-fold female DNA.

Hypervariable polymorphism of autosomal origin detected by the Y-chromosome derived probe, pHY10

A recombinant DNA probe (pHY10) hybridizing specifically to human DNA family DYZ1, 3,000 copies of which are present on the long arm of the Y chromosome, was used for probing human genome DNA digested with various restriction enzymes. To our surprise, the probe detected a hypervariable polymorphism of autosomal origin in human DNA when digested with TaqI. None of other 12 restriction enzymes revealed polymorphic patterns. Codominant segregation of the polymorphism was established in family studies. This probe has been widely used in the detection of the Y chromosome. Its ease of availability as well as highly discriminating polymorphic pattern makes it potentially very useful for forensic and human genetic purposes.