Reduced cell number in the neocortical part of the human fetal brain in Down syndrome.
Mental retardation is seen in all individuals with Down syndrome (DS) and different brain abnormalities are reported. The aim of this study was to investigate if mental retardation at least in part is a result of a lower cell number in the neocortical part of the human fetal forebrain. We therefore compared brains of DS fetuses aged 19 weeks of gestation with normal control brains. The cell numbers were estimated using the optical fractionator method. The total cell number in the neocortical part of four DS human fetal forebrain was found to be substantially smaller in DS compared to the normal fetus. The average total cell number of 6.85 billion was equal to a reduction by 34% compared to the 10.4 billion cells in a normal fetal brain of that age. This study indicates that the mental retardation found in DS is based on a structural deficit in the human fetal brain already present in the second trimester.
Larsen
Karen Bonde
KB
Research Laboratory for Stereology and Neuroscience, Bispebjerg University Hospital, Bispebjerg Bakke 23, DK-2400 Copenhagen NV, Denmark. kbondelarsen@gmail.com
Laursen
Henning
H
Graem
Niels
N
Samuelsen
Grethe Badsberg
GB
Bogdanovic
Nenad
N
Pakkenberg
Bente
B
D001344:Autopsy; D002452:Cell Count / Q000706:statistics & numerical data; D004314:Down Syndrome / Q000196:embryology* / Q000473:pathology*; D005260:Female; D005333:Fetus / Q000473:pathology*; D005865:Gestational Age; D006801:Humans; D008607:Intellectual Disability / Q000196:embryology / Q000473:pathology; D008297:Male; D019579:Neocortex / Q000196:embryology* / Q000473:pathology*; D011247:Pregnancy; D011262:Pregnancy Trimester, Second; D014793:Visual Cortex / Q000196:embryology / Q000473:pathology