Population genetic studies in Indonesia
Abstract
Some three thousand blood samples from various Indonesian populations have been tested for electrophoretic variations of 21 red cell enzymes, three serum proteins and haemoglobin. In addition G6PD deficiency was also screened in the field and red cell morphology was also examined from unstained blood films to diagnose ovalocytosis.
Among 21 red cell enzymes tested, excluding G6PD, nine enzymes were polymorphic, five showed rare variants and six were monomorphic. In serum proteins, two proteins were polymorphic and one was monomorphic. For haemoglobin, in addition to two rare abnormal haemoglobins, Hb E was polymorphic. New variants were discovered in esterase D, carbonic anhydrase 2, 6-phosphogluconate dehydrogenase and transferrin.
A clinal pattern was observed in the distribution of GLO¹, GPT ¹, PDGC and Hp¹ across the Indonesian archipelago. There is a trend of increasing GPT ¹, PDGC gene frequencies and of decreasing GLO¹ gene frequency towards the east. For systems with more specific alleles, distribution of PGM 92 and Tf D1 showed that western limit as far as Java and the distribution of Tf DChi and Hb E showed the eastern limit as far as Halmahera in the north and Timor in the south.
Variation in the red cell enzymes, serum proteins and also Hb E were used to study the genetic relationship between populations. Employing data for gene frequency distributions in the populations, Nei’s genetic distance measure was used to analyse the genetic relationship between Indonesian populations themselves and between Indonesian and neighbouring populations. A separate analysis was also made of the genetic relationship between the Balinese village populations. The results showed that Indonesian populations may be grouped into a western and eastern Indonesian cluster. The western Indonesian cluster consists of all populations of the Greater Sunda Islands and the Lesser Sunda Islands from Sumbawa to the west, while the eastern Indonesian cluster is composed of populations of the Lesser Sunda Islands beyond Sumbawa to the east and those from the Moluccas. When contrasted to the neighbouring populations, the Malays and Tagalog were grouped into the western Indonesian cluster, whereas the Fijians and Motu-speakers from Papua New Guinea were grouped into the eastern Indonesian cluster. The Asmat from Irian Jaya, Angurugu from north Australia and Kadazans from Sabah were distinctive from either cluster.
Analysis of the Balinese village populations showed that their genetic heterogeneity was compatible to some extent with geographical distance and/or topographical setting, but historical factors may also have played a part.
Examinations of blood genetic traits associated with malaria indicated that G6PD deficiency and ovalocytosis was widely distributed in the archipelago, whilst the distribution of Hb E showed an eastern limit apparently associated with more recent population migration. Interaction between G6PD deficiency and ovalocytosis shown by the inverse proportion of the respective trait was to be observed beyond Java to the east.