Sequence data from the hypervariable segments I (HVS-I) and II (HVS-II) was obtained for 30 Angolares, 35 Forros and 38 Tongas, three self-reported ethnic groups from São Tomé e Príncipe, an African archipelago (Gulf of Guinea) whose settlement begun in the late 15th century. The repertory of mtDNA lineages denoted a fully African maternal pool primarily arisen from a Central/Southwestern substratum. The absence of any lineages of putative European descent means that the European impact at the mitochondrial pool was virtually nil. Angolares showed a clear reduction of mtDNA diversity and a slight genetic differentiation relatively to Tongas or Forros, whereas the two last groups did not present any signs of genetic boundaries between each other. The data now obtained reinforce the depiction of genetic substructuring in São Tomé e Príncipe previously derived from Y-chromosome STRs.http://www.sciencedirect.com/science/article/B7581-4C4WDDP-4F/1/820043d2aef5dc67577eadeb2c4c328

Abade, Augusto

Amorim, António

Gusmão, Leonor

Pereira, Luísa

Prata, Maria João

Trovoada, Maria Jesus

Estudo Geral

www.ics-elsevier.com
International Congress Series 1261 (2004) 377–379Insights from pattern of mtDNA variation into the
genetic history of Sa˜o Tome´ e Prı´ncipe
Maria Jesus Trovoadaa,b, Luı´sa Pereiraa, Leonor Gusma˜oa,
Augusto Abadeb, Anto´nio Amorima,c, Maria Joa˜o Prataa,c,*
a IPATIMUP, Institute of Pathology and Immunology of University of Porto, Rua Dr. Roberto Frias,
s/n. 4200-465, Oporto, Portugal
bDepartment of Anthropology, University of Coimbra, Coimbra, Portugal
cFaculty of Sciences, University of Porto, Oporto, Portugal
Abstract. Sequence data from the hypervariable segments I (HVS-I) and II (HVS-II) was obtained
for 30 Angolares, 35 Forros and 38 Tongas, three self-reported ethnic groups from Sa˜o Tome´ e
Prı´ncipe, an African archipelago (Gulf of Guinea) whose settlement begun in the late 15th century.
The repertory of mtDNA lineages denoted a fully African maternal pool primarily arisen from a
Central/Southwestern substratum. The absence of any lineages of putative European descent means
that the European impact at the mitochondrial pool was virtually nil. Angolares showed a clear
reduction of mtDNA diversity and a slight genetic differentiation relatively to Tongas or Forros,
whereas the two last groups did not present any signs of genetic boundaries between each other. The
data now obtained reinforce the depiction of genetic substructuring in Sa˜o Tome´ e Prı´ncipe
previously derived from Y-chromosome STRs. D 2003 Elsevier B.V. All rights reserved.
Keywords: MtDNA; Haplogroups; Sa˜o Tome´ e Prı´ncipe; Population groups
1. IntroductionSa˜o Tome´ e Prı´ncipe is a small archipelago located on the Equator (Gulf of Guinea) that
was uninhabited when first visited by Portuguese navigators in the early 1470s. Shortly
afterward, the settlement was initiated with European colonist, mainly Portuguese, and an
overwhelming number of slaves brought from the African Western mainland.
Among present day Sa˜o Tome´ e Prı´ncipe inhabitants, the existence of three distinct
population groups, Angolares, Forros and Tongas, is a common perception. Forros are
referred to be ‘‘the sons of the land’’, the more ancient African inhabitants of the
archipelago [1]. Tongas are the descendents from African contract labourers who, from
the middle of the 19th century on with the development of the coffee and cocoa
economy, massively entered the archipelago. The origin of Angolares is less clear
notwithstanding the fact that the identification as a distinct community has the stronger0531-5131/ D 2003 Elsevier B.V. All rights reserved.
doi:10.1016/S0531-5131(03)01633-9
* Corresponding author. IPATIMUP, Institute of Pathology and Immunology of University of Porto, Rua Dr.
Roberto Frias, s/n. 4200-465, Oporto, Portugal. Tel.: +351-225570700; fax: +351-225570799.
E-mail address: mprata@ipatimup.pt (M.J. Prata).
M.J. Trovoada et al. / International Congress Series 1261 (2004) 377–379378support from the geographical confinement to the southeastern tip of Sa˜o Tome´, from
cultural and livelihood traditions or from the own language.
Here we present sequence data from mtDNA detected by surveying HVS-I and HVS-II
in individuals from the three Sa˜o Tomean groups.
2. Material and methods
Blood samples were collected from 30 self-reported Angolares, 35 Forros and 38
Tongas. DNA was extracted from whole blood by standard phenol chloroform or Chelex
methodologies. Primers, PCR and sequencing strategy as described in Ref. [2]. PCR
products purified with Microspink S-300 HR columns (Pharmacia). Sequence reactions
carried out with the kit Big-Dyek Terminator Cycle Sequencing Ready Reaction (AB
Applied Biosystems) and then a protocol based on MgCl2/ethanol precipitation for
purification of samples. Automatic sequencer: ABI Prism 3100 Genetic Analyzer.
Sequence analysis: DNA Sequencing Analysis 3.7 software (AB Applied Biosystems).
3. Results and discussion
Among the 103 Sa˜o Tomeans analysed, 71 different sequences were found (Fig. 1)
belonging to 32 distinct haplogroups all specific from sub-Sahara, which testifies a full
matrilineal African background. Previously we have detected some Y-STR haplotypes of
likely European ancestry [3]. The combined results indicate that the European component
of present Sa˜o Tome´ e Prı´ncipe population was essentially mediated by males, signalling
therefore the biased mating pattern that has prevailed in the archipelago.
Within the overall sample, four haplogroups, L1b, L1c, L2a1 and L3e1*, attained
considerable high frequencies representing 56% of the sequences. The four haplogroups
are common in West/Central Africa. Forros and Tongas, basically share the same mtDNA
profile characterised by the presence of many different haplogroups. In contrast, the
Angolares show a reduced number of different haplogroups and a particularly high
frequency of L3e1* and L1c lineages.
Diversity levels in Forros, Tongas and in the overall Sa˜o Tomean sample (Table 1) are
very similar to those registered in mainland populations from the cluster of Central/
Western ones at which Sa˜o Tome´ e Prı´ncipe geographically belongs. Distinctly, Angolares
show lower diversity, particularly concerning mean heretozygosity and proportion of
different haplotypes, resembling what happens in Western African islands such as Cabo
Verde NW or Bioko.Fig 1. mtDNA haplogroup profiles in Angolares, Forros, Tongas and in overall Sa˜o Tome´.
Table 1
Diversity and neutrality measures for HVS-I in African populations
Population/group N a K (K/N)b H (S.E.)c Md Fu’s Fs
Morocco [4] 32 29 (90.6) 0.988F 0.014 5.84  25.01*
Niger [5] 34 30 (88.3) 0.991F 0.010 6.19  24.70*
Nigeria [5] 60 38 (63.3) 0.972F 0.010 6.82  23.15*
Senegal [6] 110 46 (41.8) 0.963F 0.008 6.23  24.53*
C.Verde NW [7] 108 28 (25.9) 0.908F 0.013 5.84  5.58
C.Verde SE [7] 184 101 (54.9) 0.984F 0.003 6.29  24.85*
Mbuti [8] 13 5 (38.5) 0.756F 0.097 7.13 3.76
Biaka [8] 17 8 (47.1) 0.890F 0.043 7.81 1.67
Bioko [9] 45 16 (35.6) 0.910F 0.020 7.09  0.55
Angolares 30 16 (53.5) 0.913F 0.037 8.74  1.34
Forros 35 29 (82.9) 0.988F 0.010 7.52  18.66*
Tongas 38 28 (73.7) 0.984F 0.009 8.55  12.61*
Sa˜o Tome´ 103 61 (59.2) 0.985F 0.004 8.36  24.68*
Kenya [4] 36 32 (88.9) 0.991F 0.010 9.66  20.75*
Mozambique [2] 109 49 (45.0) 0.960F 0.008 7.78  23.62*
a N = sample size. b K= number of different sequences and percentage of sample size (N). c H = sequence diversityF
standard error. d M = average number of pairwise differences.
*P< 0.05.
M.J. Trovoada et al. / International Congress Series 1261 (2004) 377–379 379Analysis of population pairwise FSTs revealed statistically significant differences
between Angolares and Forros (FST = 0.037, P = 0.04) or Angolares and Tongas
(FST= 0.030, P= 0.04); while Tongas and Forros did not showed statistical differences
(FST= 0.01, P= 0.14). The small level of genetic distinctiveness of Angolares can be
attributable to genetic drift since, until recently, they lived in relative isolation in the
southeastern tip of Sa˜o Tome´ e Prı´ncipe, which is also reflected in their cultural and
livelihood traditions or even in their own language.
For a small archipelago with a so recent population history, this is really a quite
remarkable finding. In Sa˜o Tome´ e Prı´ncipe, a complex net of social and historical forces
must have interacted in order that a self-reported community like Angolares, with a
presumable distinct origin from other Sa˜o Tome´ e Prı´ncipe inhabitants, has retained and
still preserves signs of genetic distinctiveness, despite the sharing of a so restricted territory
with other people.
Acknowledgements
Financial support was granted by Fundaca˜o para a Cieˆncia e a Tecnologia, Programa
Operacional Cieˆncia, Tecnologia e Inovaca˜o (POCTI).
References
[1] I.C. Henriques, Sa˜o Tome´ e Prı´ncipe. A invenca˜o de uma sociedade, Vega e Autor, 2000.
[2] L. Pereira, et al., Ann. Hum. Genet. 65 (2001) 439–458.
[3] M.J. Trovoada, et al., Ann. Hum. Genet. 65 (2001) 271–283.
[4] J.C. Rando, et al., Ann. Hum. Genet. 62 (1998) 531–550.
[5] E. Watson, et al., Am. J. Hum. Genet. 61 (1997) 691–704.
[6] L. Graven, et al., Mol. Biol. Evol. 12 (1995) 334–345.
[7] A. Brehm, et al., Ann. Hum. Genet. 66 (2002) 49–60.
[8] L. Vigilant, et al., Science 253 (1991) 1503–1507.
[9] E. Mateu, et al., Ann. Hum. Genet. 61 (1997) 507–518.


Insights from pattern of mtDNA variation into the genetic history of São Tomé e Príncipe

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Insights from pattern of mtDNA variation into the genetic history of São Tomé e Príncipe

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