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Hochstenbach R, Nowakowska B, Volleth M, Ummels A, Kutkowska-Kaźmierczak A, Obersztyn E, Ziemkiewicz K, Gerloff C, Schanze D, Zenker M, Muschke P, Schanze I, Poot M, Liehr T. Multiple Small Supernumerary Marker Chromosomes Resulting from Maternal Meiosis I or II Errors. Mol Syndromol 2016; 6:210-21. [PMID: 26997941 PMCID: PMC4772618 DOI: 10.1159/000441408] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/16/2015] [Indexed: 01/11/2023] Open
Abstract
We present 2 cases with multiple de novo supernumerary marker chromosomes (sSMCs), each derived from a different chromosome. In a prenatal case, we found mosaicism for an sSMC(4), sSMC(6), sSMC(9), sSMC(14) and sSMC(22), while a postnatal case had an sSMC(4), sSMC(8) and an sSMC(11). SNP-marker segregation indicated that the sSMC(4) resulted from a maternal meiosis II error in the prenatal case. Segregation of short tandem repeat markers on the sSMC(8) was consistent with a maternal meiosis I error in the postnatal case. In the latter, a boy with developmental/psychomotor delay, autism, hyperactivity, speech delay, and hypotonia, the sSMC(8) was present at the highest frequency in blood. By comparison to other patients with a corresponding duplication, a minimal region of overlap for the phenotype was identified, with CHRNB3 and CHRNA6 as dosage-sensitive candidate genes. These genes encode subunits of nicotinic acetylcholine receptors (nAChRs). We propose that overproduction of these subunits leads to perturbed component stoichiometries with dominant negative effects on the function of nAChRs, as was shown by others in vitro. With the limitation that in each case only one sSMC could be studied, our findings demonstrate that different meiotic errors lead to multiple sSMCs. We relate our findings to age-related aneuploidy in female meiosis and propose that predivision sister-chromatid separation during meiosis I or II, or both, may generate multiple sSMCs.
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Affiliation(s)
- Ron Hochstenbach
- Division of Biomedical Genetics, Department of Medical Genetics, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Beata Nowakowska
- Department of Medical Genetics, Institute of the Mother and Child, Warsaw, Poland
| | | | - Amber Ummels
- Division of Biomedical Genetics, Department of Medical Genetics, University Medical Center Utrecht, Utrecht, The Netherlands
| | | | - Ewa Obersztyn
- Department of Medical Genetics, Institute of the Mother and Child, Warsaw, Poland
| | - Kamila Ziemkiewicz
- Department of Medical Genetics, Institute of the Mother and Child, Warsaw, Poland
| | - Claudia Gerloff
- University Women's Clinic, Otto-von-Guericke University, Magdeburg, Germany
| | | | | | | | - Ina Schanze
- Department of Human Genetics, Magdeburg, Germany
| | - Martin Poot
- Division of Biomedical Genetics, Department of Medical Genetics, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Thomas Liehr
- Department of Human Genetics, University Clinic, Jena, Germany
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Abstract
Basal forebrain cholinergic neurons constitute a way station for many ascending and descending pathways. These cholinergic neurons have a role in eliciting cortical activation and arousal. It is well established that they are mainly involved in cognitive processes requiring increased levels of arousal, attentive states and/or cortical activation with desynchronized activity in the EEG. These cholinergic neurons are modulated by several afferents of different neurotransmitter systems. Of particular importance within the cortical targets of basal forebrain neurons is the hippocampal cortex. The septohippocampal pathway is a bidirectional pathway constituting the main septal efferent system, which is widely known to be implicated in every memory process investigated. The present work aims to review the main neurotransmitter systems involved in modulating cognitive processes related to learning and memory through modulation of basal forebrain neurons.
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