Introducing ourselves

The Hemoglobinopathy Laboratory at the Dept. of Human and Clinical Genetics at the Leiden University Medical Center is reference laboratory for research, diagnosis and prevention of the hemoglobinopathies (HbP's).

The Hemoglobinopathies laboratory has a good international reputation in the field of a- and b- globin gene defects analyses at the hematological, biochemical, and molecular level in mixed populations in which many different HbP mutations occur.


Some history

The Hemoglobinopathies Laboratory took form in the Biochemical Genetics group which for many years was guided by Professor L. F. Bernini, within the former Department of Human Genetics (Anthropogenetica, Leiden). Today we are a section of the Center of Human and Clinical Genetics, which is guided by Professor G-J. B. van Ommen and Professor M. Breuning respectively.

The Biochemical Genetics group has been active on research and diagnostics of hemoglobinopathies and thalassemias since the mid-sixties. Research first done at the population- and hematological levels, then at the protein-, and later at the molecular levels. The group has been involved in the determination of gene-frequencies in several world populations and in the development of prevention strategies in the Mediterranean countries. Presently we are concerned with diagnostics and prevention in emerging countries and in industrialized areas with high concentrations of multi-ethnic populations at risk.


Permanent group members:

Our Hemoglobinopathies lab consists of the staff, Dr. C.L. Harteveld Assistent Professor, clinical biochemical molecular geneticist (head) and Dr. P.C. Giordano Ph.D, emeritus Ass. Prof. clinical biochemical molecular geneticist (advisor), and three senior technicians, Ing. P. van Delft, S. Arkesteijn and S. Broekman, four technicians, Ing. G. Bakker-Verwey, F. Kok, M. Geerts and R. Schaap. Our group is completed by trainees and guests, who conduct their research in our laboratory, and a few enthousiastic trainees from both health sciences and HLO.


Research on techniques development, diagnostics, and prevention:

  • At the end of the eighties and the beginning of the nineties, Denaturing Gradient Gel Electrophoresis (DGGE) was made applicable for the detection of point mutations causing b-thalassemia in the allochthonous and autochthonous Dutch population (Ph.D. thesis "Structure and expression of the b-globin gene cluster" by M. Losekoot, 1990). International courses were organized in 1992 (Leiden) and 1994 (Bangkok) to distribute knowledge about the application of these techniques in hemoglobinopathy diagnostics to post-academic students and professionals working in the field.
  • In the mid-nineties, DGGE and Single Strand Conformation Analysis (SSCA) were applied for the detection of point mutations causing a-thalassemia in the multiethnic Dutch population (Ph.D thesis "The molecular genetics of a-thalassemia" by C.L.Harteveld, 1998).
  • Fundamental research topics involved the structure and evolution of multi-gene families using the haptoglobin-, a- and b-globin gene clusters as a model (Ph.D. thesis "Evolution of multigene families: hemoglobins and haptoglobins" by R. Fodde, 1990) and the characterization of the upstream flanking genes of the human and mouse a-globin gene cluster (Ph.D. thesis "The a-globin domain of man and mouse" by M.F.Kielman, 1996).
  • Extended knowledge about the mutation spectrum of HbP's and diagnosis of complex combinations of defects are indispensable for prevention. Preconceptional carrier-detection, prenatal diagnosis and information are essential elements to be able to offer prevention of severe forms of HbP's to couples at-risk in the Dutch population (Ph.D thesis "Hemoglobinopathieën in Nederland, diagnostiek, epidemiologie en preventie" van P.C.Giordano, 1998).

Prevention oriented research:

Applied research for diagnostics and prevention of HbP's in the Dutch population at risk
Summary: Although the diagnostic and counselling possibilities currently available in The Netherlands are adequate, they are scarcely utilized for appropriate prevention. The at least 140,000 HbP carriers present in the last 3 generations of the Dutch immigrant population have either not been diagnosed or are insufficiently informed concerning the genetic risk of their traits.
The risk for homozygous or compound heterozygous progeny in ethnic minorities remains virtually as high as in the country of origin. This because the choice of the partner in mainly restricted to the own ethnic group and is often inter familiar. Furthermore, the reproductive rate of immigrant populations is usually higher than the native average, therefore more children affected with severe forms of hemoglobinopathies can also be expected in these communities.
Prevention by prenatal diagnosis requires information, carrier diagnostics, and in the end a suitable protocol and knowledge about the molecular defects present in the country. Therefore, a large number of patients and carriers have been analyzed, both at the hematological and at the DNA level, in order to define the mutations spectrum present in the multiethnic Dutch population. Information and carrier detection based on standard hematological analysis, and appropriate counselling are the steps that must be taken for prevention of hemoglobinopathies in The Netherlands.


What is done: In planning an appropriate prevention protocol for the Dutch population, three main problems must be overcome:
  1. The development of a suitable strategy for a rapid hematological and molecular analysis of the many different defects expected from the multiethnic Dutch population.
  2. The definition of the molecular spectrum of the defects expected in the country.
  3. The implementation of a diagnostic procedure based on carrier detection, information, and partner/family analysis.
The first two problems have been addressed by Giordano [1994] Losekoot et al. [1990], and Harteveld et al. [1996]. To addressing the second problem, a large population sample consisting of patients, usually referred to our laboratory for some hematological anomaly, were analysed. Specific hematological analysis was performed on more than 3.000 individuals. About 1000 patients who had been diagnosed for hemoglobinopathy-trait were approached and asked for cooperation in a molecular screening project. A total of 253 independent propositi with various genotypes resulted in 308 independent chromosomes with the most common abnormal hemoglobin variants. A total of 275 independent b-thalassemia chromosomes were studied revealing 53 different mutations to date (Giordano et al. 1999).


What must still be done: The third problem still needs a great deal of attention. While homozygous or compound heterozygous patients are easily recognised, only a minor proportion of heterozygotes are actually detected because of their minor clinical symptoms. Hence, carrier detection on an individual basis is needed (Giordano & Harteveld 1998, Giordano 1999).


Ongoing and future research projects:
  • Development of a DNA-chip for the detection of point mutations causing b-thalassemia in the Dutch population as a model and possibly for practical application in prenatal diagnosis.
  • Detection of foetal cells in maternal circulation for use of prenatal diagnostics.
  • Development of strategies for diagnosis and prevention in countries with a high incidence of Hb-pathies by determining the molecular spectrum of point mutations. Depending on the molecular spectrum, the most efficient point mutation detection assay can be selected, for example (combinations of) restriction enzyme analysis, DGGE, Reverse-dotblot- or DNA-chip analysis.
  • Determining the molecular spectrum of b- and a-thalassemia in developing countries.
  • Research involving elevation of HbF expression as a therapy to ameliorate the effects of severe anaemia and sickling in b-thalassemia-major and Sickle cell disease, respectively. Study the effects of haplotype on HbF expression levels in heterozygous and homozygous b-thalassemia patients with high HbF expression both in vivo an in vitro.
  • In vitro testing of sicklecell formation and inhibition of HbS polymerisation in the red cell.


Goals:
  • The application of a proper prevention protocol for the Dutch population for the severe forms of hemoglobinopathies by carrier-detection, by offering the couples at risk the possibility of informed consent.
  • The development of techniques and strategies for the detection of point mutations and deletions causing a- and b-thalassemia.
  • Expression studies of the a- and b-globin gene clusters.
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