Deficient arylsulfatase A activity causes the neurodegenerative disease metachromatic leukodystrophy. However, some individuals with deficient enzyme activity appear clinically normal. This "pseudodeficiency" allele commonly found among many reported populations (frequency approximately 0.10) is associated with two A-->G transitions in cis in the arylsulfatase A gene causing the simultaneous loss of an N-glycosylation and a polyadenylation signal. To understand the evolutionary relationship between such common and tightly linked mutations, we studied 400 individuals in the African, European, Indian and East Asian populations and found none carrying the polyadenylation mutation alone. However, the N-glycosylation mutation could occur independently. Its frequency varied from 0.01 in Indians, 0.06 in Europeans, 0.21 in East Asians to 0.32 in Africans. The frequencies of both mutations occurring together ranged from almost non-existent in the Africans and East Asians, to 0.075 in the Europeans and 0.125 in the Indians. These frequencies were significantly different among populations. Haplotype analysis among homozygous pseudodeficiency individuals and eight multi-generation families with six polymorphic enzymes showed that, of the five haplotypes found in the general population, only one was linked to the double mutations. Alleles among the four populations with only the N-glycosylation mutation also supported linkage to the same haplotype except in some Europeans whose alleles were discordant. These results are consistent with the hypothesis that the N-glycosylation mutation may be a recurrent event among the Europeans but first occurred in an ancestral allele before the emergence of modern Homo sapiens from Africa at approximately 100,000-200,000 years ago. Subsequently, the polyadenylation mutation occurred in this ancient allele with the N-glycosylation mutation, an event that likely took place after the divergence between the European and East Asian lineages.
PMID: 9402957, UI: 98066661 IEEE Eng Med Biol Mag 1997 Sep;16(5):145-150
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A potentially cost-effective strategy for gene therapy of hemophilia B is to create universal factor IX-secreting cell lines suitable for implantation into different patients. To avoid graft rejection, the implanted cells are enclosed in alginate-polylysine-alginate microcapsules that are permeable to factor IX diffusion, but impermeable to the hosts' immune mediators. This nonautologous approach was assessed by implanting encapsulated mouse myoblasts secreting human factor IX into allogeneic mice. Human factor IX was detected in the mouse plasma for up to 14 days maximally at approximately 4 ng/mL. Antibodies to human factor IX were detected after 3 weeks at escalating levels, which were sustained throughout the entire experiment (213 days). The antibodies accelerated the clearance of human factor IX from the circulation of the implanted mice and inhibited the detection of human factor IX in the mice plasma in vitro. The encapsulated myoblasts retrieved periodically from the implanted mice up to 213 days postimplantation were viable and continued to secrete human factor IX ex vivo at undiminished rates, hence suggesting continued factor IX gene expression in vivo. Thus, this allogeneic gene therapy strategy represents a potentially feasible alternative to autologous approaches for the treatment of hemophilia B.
PMID: 8652822, UI: 96247511
Hum Gene Ther 1996 Jan;7(1):61-70
Recently, we have succeeded in using nonautologous myoblasts engineered to secrete mouse growth hormone (GH) to correct partially the growth retardation of the Snell dwarf mice, which suffer from pituitary GH deficiency. The allogeneic myoblasts were protected from immune rejection by enclosure in permselective microcapsules fabricated from alginate, thus validating the clinical efficacy of using universal nonautologous cells for somatic gene therapy. Because GH therapy is considered also for treating patients with normal pituitary function, we now apply this protocol to treat normal mice to evaluate the potential consequences of using GH gene therapy in subjects with no demonstrated GH deficiency. When microencapsulated allogeneic myoblasts engineered to secrete mouse GH were implanted into normal male and female mice, contrary to expectation, the treated animals became significantly shorter and lost weight; their internal organs became smaller and their tibial growth plates were less differentiated, indicating reduced skeletal growth. Females were more severely affected than males and 2 animals died by day 13 of unknown cause. By day 70, most of the abnormalities were restored to normal except for body weights, which remained below normal. In conclusion, although somatic gene therapy for GH delivery is beneficial for pituitary dwarfism, it may have adverse metabolic consequences in those with normal hypothalamic-pituitary functions, and the female mice were more severely affected than males.
PMID: 8825869, UI: 96423268