First Unaffected Pregnancy Using Preimplantation Genetic Diagnosis for Sickle Cell Anemia
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ORIGINAL CONTRIBUTION First Unaffected Pregnancy Using Preimplantation Genetic Diagnosis for Sickle Cell Anemia Kangpu Xu, PhD Context Sickle cell anemia is a common autosomal recessive disorder. However, pre- Zhong Ming Shi, MD implantation genetic diagnosis (PGD) for this severe genetic disorder previously has not been successful. Lucinda L. Veeck, MLT, DSc Objective To achieve pregnancy with an unaffected embryo using in vitro fertiliza- Mark R. Hughes, MD, PhD tion (IVF) and PGD. Zev Rosenwaks, MD Design Laboratory analysis of DNA from single cells obtained by biopsy from em- ICKLE CELL ANEMIA IS ONE OF THE bryos in 2 IVF attempts, 1 in 1996 and 1 in 1997, to determine the genetic status of each embryo before intrauterine transfer. most common human autoso- mal recessive disorders. It is Setting University hospital in a large metropolitan area. caused by a mutation substitut- Patients A couple, both carriers of the recessive mutation for sickle cell disease. Sing thymine for adenine in the sixth Interventions Standard IVF treatment, intracytoplasmic sperm injection, embryo bi- codon (GAG to GTG) of the gene for the opsy, single-cell polymerase chain reaction and DNA analyses, embryo transfer to uterus, b-globin chain on chromosome 11p, pregnancy confirmation, and prenatal diagnosis by amniocentesis at 16.5 weeks’ ges- thereby encoding valine instead of glu- tation. tamic acid in the sixth position of the Main Outcome Measure DNA analysis of single blastomeres indicating whether globin chain. The frequency of sickle cell embryos carried the sickle cell mutation, allowing only unaffected or carrier embryos trait (carrier status) among the African to be transferred. American population at birth is about Results The first IVF attempt failed to produce a pregnancy. Of the 7 embryos ana- 8%, and the incidence of sickle cell ane- lyzed in the second attempt, PGD indicated that 4 were normal and 2 were carriers; mia at birth is 0.16%, or 1 per 625 diagnosis was not possible in 1. Three embryos were transferred to the uterus on the births.1 Furthermore, the widespread fourth day after oocyte retrieval. A twin pregnancy was confirmed by ultrasonogra- presence of the sickle gene in other eth- phy, and subsequent amniocentesis revealed that both fetuses were unaffected and nic groups has also been confirmed.2 For were not carriers of the sickle cell mutation. The patient delivered healthy twins at 39 example, in urban centers in the United weeks’ gestation. States, nearly 10% of patients with vari- Conclusion This first unaffected pregnancy resulting from PGD for sickle cell ane- ous sickling disorders identify them- mia demonstrates that the technique can be a powerful diagnostic tool for carrier couples selves as non–African American.3 who desire a healthy child but wish to avoid the difficult decision of whether to abort Children affected with sickle cell ane- an affected fetus. mia experience recurrent episodes of pain JAMA. 1999;281:1701-1706 www.jama.com (during sickle cell crises) and increased rican American children aged 1 to 4 years Author Affiliations: The Center for Reproductive susceptibility to potentially life- due to sickle cell disease.4 Life expec- Medicine and Infertility and the Department of Ob- threatening conditions, including bac- stetrics and Gynecology, Weill Medical College of Cor- tancy for persons with sickle cell dis- terial infections, cerebrovascular acci- nell University, New York, NY (Drs Xu, Shi, Veeck, and ease varies and there is an age-related Rosenwaks); and the Department of Reproductive Ge- dents, and organ failure. According to US pattern in mortality rates: a peak in pa- netics, Wayne State University, Detroit Medical Cen- statistics collected between 1981 and ter, Detroit, Mich (Dr Hughes). tients younger than 5 years, with a 1992, there were 6.8 deaths per 1000 Af- Corresponding Author and Reprints: Zev Rosen- gradual increase starting in late adoles- waks, MD, The Center for Reproductive Medicine and 5 Infertility, Weill Medical College of Cornell Univer- cence. Progress in the treatment of sickle sity, 505 E 70th St, Room HT326a, New York, NY See also Patient Page. 6 cell disease has been slow. At present, 10021 (e-mail: [email protected]). ©1999 American Medical Association. All rights reserved. JAMA, May 12, 1999—Vol 281, No. 18 1701 Downloaded From: https://jamanetwork.com/ on 09/23/2021 PREIMPLANTATION DIAGNOSIS FOR SICKLE CELL ANEMIA there is no satisfactory treatment for the because she was carrying fetuses af- digested with the restriction enzyme sickling condition, although blood trans- fected with sickle cell anemia. Genetic DdeI (GIBCO/BRL, Rockville, Md) for fusion may reduce the risk of a first stroke diagnosis indicated that both female and 3 hours. Subsequently, 10 µL of di- in children7 and gene therapy holds male partners were carriers of the sickle gested product was run on a 10% acryl- promise for a curative approach.8 cell mutation. After extensive counsel- amide gel. On completion of electro- Early prenatal diagnosis of the dis- ing, the couple gave informed consent phoresis, the gel was stained with ease is critical because it allows a couple and elected to undergo preimplanta- ethidium bromide and photographed by to consider pregnancy termination as tion genetic diagnosis. The study was UV transillumination. As predicted, un- an option. The first DNA diagnostic approved by the Weill Medical Col- affected DNA showed 3 bands (201, 90, procedure for prenatal purposes was re- lege of Cornell University (New York, and 74 base pairs [bp]), carrier DNA ported 20 years ago.9 Subsequently, it NY) Institutional Review Board. showed 4 bands (291, 201, 90, and 74 was recognized that the mutation it- To confirm the genetic status of the bp), and an affected homozygous self affected the cleavage site of a re- couple and establish a protocol for sample showed only 2 bands (291 and striction enzyme, DdeI, that could rec- single-copy gene amplification from 74 bp). Testing of single lymphocytes ognize the DNA sequence of CTNAG single cells, blood was collected from from the male and female subjects (N = A, T, C, or G). While DNA from a both partners. Lymphocytes were iso- showed the same predicted patterns (4 normal allele (CTGAG) would be di- lated using Ficoll-Paque density gradi- bands of predicted sizes), together with gested by the enzyme, DNA from an af- ent separation (Pharmacia Biotech Inc, an unaffected DNA control (3 bands) fected allele in which A is substituted Piscataway, NJ) with the protocol pro- (FIGURE 1). by T (CTGTG) would not.10,11 The re- vided by the manufacturer. Single lym- The IVF procedure has been de- sulting differences between DNA frag- phocytes were loaded into 0.5-mL tubes scribed previously.20 Briefly, to ensure ment sizes can then be recognized by containing 5 µL of lysis buffer19 and that several embryos would become electrophoresis, thus forming the ba- stored at −20°C before trial testing. available for DNA analysis, multiple sis for diagnosis. With the advent of On the day of preliminary trial test- ovarian follicular development was ini- polymerase chain reaction (PCR), rapid ing, sample tubes were removed from the tiated with gonadotropin therapy. Af- DNA analysis methods have become freezer and heated to 65°C for 10 min- ter pituitary desensitization with go- available, and these techniques are now utes before they were placed back on ice. nadotropin hormone–releasing widely used for prenatal diagnosis.12-16 Five microliters of neutralization buffer hormone agonist (leuprolide acetate, An alternative and powerful diagnos- was added to each tube. A nested PCR TAP Pharmaceutical, Chicago, Ill), tic tool for identifying sickle cell status approach was used for the amplifica- ovarian stimulation was begun on day in embryos is preimplantation genetic di- tion of the region surrounding the sickle 3 of the ensuing menstrual cycle using agnosis (PGD), which became possible cell mutation. The primers used have intramuscular administration of a com- nearly a decade ago.17 Preimplantation been described previously.17,19 Polymer- bination of urofollitropin (75 U of genetic diagnosis takes advantage of as- ase chain reaction was performed after pure follicle-stimulating hormone) sisted reproductive techniques in con- adding a standard mixture of all com- and menotropins (150 U of follicle- junction with modern molecular meth- ponents, including 2.5 mmol of Mg2+, 0.2 stimulating hormone and luteinizing ods. With PGD, the genetic status of an mmol of dNTPs (containing dATP, hormone) (Serono Laboratories, Nor- embryo can be determined before trans- dCTP, dGTP, and dTTP, Perkin Elmer, well, Mass). Follicular growth was fer into the uterus after in vitro fertiliza- Foster City, Calif), 100 ng of primers, monitored by daily serum estradiol lev- tion (IVF), thus eliminating the risks of and2UofTaqpolymerase (AmpliTaq, els and pelvic ultrasonograms. To in- bearing a child with the disease. Perkin-Elmer). A hot start at 95°C was duce final oocyte maturation, 3300 IU While PGD for sickle cell anemia has applied for 3 minutes to ensure com- of human chorionic gonadotropin was been performed in the mouse model,18 plete denaturation of the template. For administered when 2 follicles of 18 mm routine clinical application in the hu- the PCR profile, the following param- in average diameter were observed on man previously has not been success- eters were used: 93°C denaturation for ultrasonogram. Transvaginal oocyte re- ful. In this article, we describe our ex- 30 seconds; 50°C for 40 seconds for an- trieval was performed 35 hours later. perience using PGD to determine the nealing; and 72°C for 45 seconds for ex- To avoid sperm contamination and pos- precise genetic status of embryos gen- tension. A total of 20 amplification cycles sible amplification of sperm DNA, in- erated by assisted reproduction for a were applied for outer primers.