Exploring copy number variants in deceased fetuses and neonates with abnormal vertebral patterns and cervical ribs.

Background: Cervical patterning abnormalities are rare in the general population, but one variant, cervical ribs, is particularly common in deceased fetuses and neonates. The discrepancy between the incidence in the general population and early mortality is likely due to indirect selection against cervical ribs. The cause for the co-occurrence of cervical ribs and adverse outcome remains unidentified.

Increased prevalence of abnormal vertebral patterning in fetuses and neonates with trisomy 21.

Purpose: To assess the prevalence of an abnormal number of ribs in a cohort of fetuses and neonates with trisomy 21 and compare this with a subgroup of fetuses without anomalies.

Materials And Methods: Radiographs of 67 deceased fetuses, neonates, and infants that were diagnosed with trisomy 21 were reviewed. Terminations of pregnancy were included.

Adverse Fetal and Neonatal Outcome and an Abnormal Vertebral Pattern: A Systematic Review.

Importance: The human vertebral column has a stable number of vertebrae and ribs, which is presumably the result of evolutionary selection. An association between an abnormal vertebral pattern, especially in the cervical region, and congenital anomalies or adverse fetal outcome has been reported.

Objective: The aim of this study was to review the current literature concerning an abnormal vertebral pattern and prevalence of cervical ribs in healthy subjects and in subjects with adverse outcome.

Fast running restricts evolutionary change of the vertebral column in mammals.

The mammalian vertebral column is highly variable, reflecting adaptations to a wide range of lifestyles, from burrowing in moles to flying in bats. However, in many taxa, the number of trunk vertebrae is surprisingly constant. We argue that this constancy results from strong selection against initial changes of these numbers in fast running and agile mammals, whereas such selection is weak in slower-running, sturdier mammals.

Extraordinary incidence of cervical ribs indicates vulnerable condition in Late Pleistocene mammoths.

The number of cervical vertebrae in mammals is highly conserved at seven. We have shown that changes of this number are selected against due to a coupling with major congenital abnormalities (pleiotropic effects). Here we show that the incidence of abnormal cervical vertebral numbers in Late Pleistocene mammoths from the North Sea is high (33.

Higher limb asymmetry in deceased human fetuses and infants with aneuploidy.

Aneuploidies cause gene-dosage imbalances that presumably result in a generalized decreased developmental homeostasis, which is expected to be detectable through an increase in fluctuating asymmetry (FA) of bilateral symmetric traits. However, support for the link between aneuploidy and FA is currently limited and no comparisons among different aneuploidies have been made. Here, we study FA in deceased human fetuses and infants from a 20-year hospital collection.

Evo-Devo of the Human Vertebral Column: On Homeotic Transformations, Pathologies and Prenatal Selection.

Homeotic transformations of vertebrae are particularly common in humans and tend to come associated with malformations in a wide variety of organ systems. In a dataset of 1,389 deceased human foetuses and infants a majority had cervical ribs and approximately half of these individuals also had missing twelfth ribs or lumbar ribs. In ~10 % of all cases there was an additional shift of the lumbo-sacral boundary and, hence, homeotic transformations resulted in shifts of at least three vertebral boundaries.

Sexual dimorphism in the prenatal digit ratio (2D:4D).

The second to fourth digit ratio (2D:4D) is smaller in human males than in females and hence this trait is sexually dimorphic. The digit ratio is thought to be established during early prenatal development under the influence of prenatal sex hormones. However, the general assumption of early establishment has hardly been studied.

Fluctuating asymmetry does not consistently reflect severe developmental disorders in human fetuses.

Developmental instability (DI), as measured by fluctuating asymmetry (FA), may reflect fitness and facilitate the expression of morphological variation. Insights in the underlying mechanisms and magnitude of DI during early development would increase our understanding of its role in evolutionary biology. We studied associations between FA and congenital abnormalities of different origins and functional systems in deceased human fetuses.

No association between fluctuating asymmetry in highly stabilized traits and second to fourth digit ratio (2D:4D) in human fetuses.

Recent studies have suggested that the ratio of the length of the second and fourth digit (2D:4D) may be associated with developmental instability (DI) as measured by the left-right asymmetry of the same digits. Because the 2D:4D ratio is amongst others, determined prenatally as a result of exposure to sex hormones, such an association could indicate that the same prenatal developmental processes determine levels of DI. In this study we criticize these earlier findings and show by simulations that they are confounded by the fact that (non-) linear combinations of the digit lengths are used as both dependent (average asymmetry in digits 2 and 4) and independent (ratio of the lengths of digits 2 and 4) variable.