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. 2018 May 3;102(5):985-994.
doi: 10.1016/j.ajhg.2018.03.004. Epub 2018 Apr 12.

Truncating Variants in NAA15 Are Associated with Variable Levels of Intellectual Disability, Autism Spectrum Disorder, and Congenital Anomalies

Hanyin Cheng  1 Avinash V Dharmadhikari  1 Sylvia Varland  2 Ning Ma  3 Deepti Domingo  4 Robert Kleyner  5 Alan F Rope  6 Margaret Yoon  5 Asbjørg Stray-Pedersen  7 Jennifer E Posey  8 Sarah R Crews  9 Mohammad K Eldomery  8 Zeynep Coban Akdemir  8 Andrea M Lewis  10 Vernon R Sutton  8 Jill A Rosenfeld  8 Erin Conboy  11 Katherine Agre  11 Fan Xia  12 Magdalena Walkiewicz  13 Mauro Longoni  14 Frances A High  15 Marjon A van Slegtenhorst  16 Grazia M S Mancini  16 Candice R Finnila  17 Arie van Haeringen  18 Nicolette den Hollander  18 Claudia Ruivenkamp  18 Sakkubai Naidu  19 Sonal Mahida  19 Elizabeth E Palmer  20 Lucinda Murray  21 Derek Lim  22 Parul Jayakar  23 Michael J Parker  24 Stefania Giusto  25 Emanuela Stracuzzi  25 Corrado Romano  25 Jennifer S Beighley  26 Raphael A Bernier  26 Sébastien Küry  27 Mathilde Nizon  27 Mark A Corbett  28 Marie Shaw  28 Alison Gardner  28 Christopher Barnett  29 Ruth Armstrong  30 Karin S Kassahn  31 Anke Van Dijck  32 Geert Vandeweyer  32 Tjitske Kleefstra  33 Jolanda Schieving  33 Marjolijn J Jongmans  33 Bert B A de Vries  33 Rolph Pfundt  33 Bronwyn Kerr  34 Samantha K Rojas  35 Kym M Boycott  35 Richard Person  36 Rebecca Willaert  36 Evan E Eichler  37 R Frank Kooy  32 Yaping Yang  12 Joseph C Wu  3 James R Lupski  38 Thomas Arnesen  39 Gregory M Cooper  17 Wendy K Chung  40 Jozef Gecz  41 Holly A F Stessman  9 Linyan Meng  42 Gholson J Lyon  43
Affiliations

Truncating Variants in NAA15 Are Associated with Variable Levels of Intellectual Disability, Autism Spectrum Disorder, and Congenital Anomalies

Hanyin Cheng et al. Am J Hum Genet. .

Abstract

N-alpha-acetylation is a common co-translational protein modification that is essential for normal cell function in humans. We previously identified the genetic basis of an X-linked infantile lethal Mendelian disorder involving a c.109T>C (p.Ser37Pro) missense variant in NAA10, which encodes the catalytic subunit of the N-terminal acetyltransferase A (NatA) complex. The auxiliary subunit of the NatA complex, NAA15, is the dimeric binding partner for NAA10. Through a genotype-first approach with whole-exome or genome sequencing (WES/WGS) and targeted sequencing analysis, we identified and phenotypically characterized 38 individuals from 33 unrelated families with 25 different de novo or inherited, dominantly acting likely gene disrupting (LGD) variants in NAA15. Clinical features of affected individuals with LGD variants in NAA15 include variable levels of intellectual disability, delayed speech and motor milestones, and autism spectrum disorder. Additionally, mild craniofacial dysmorphology, congenital cardiac anomalies, and seizures are present in some subjects. RNA analysis in cell lines from two individuals showed degradation of the transcripts with LGD variants, probably as a result of nonsense-mediated decay. Functional assays in yeast confirmed a deleterious effect for two of the LGD variants in NAA15. Further supporting a mechanism of haploinsufficiency, individuals with copy-number variant (CNV) deletions involving NAA15 and surrounding genes can present with mild intellectual disability, mild dysmorphic features, motor delays, and decreased growth. We propose that defects in NatA-mediated N-terminal acetylation (NTA) lead to variable levels of neurodevelopmental disorders in humans, supporting the importance of the NatA complex in normal human development.

Keywords: N-terminal acetylation (NTA); N-terminal acetyltransferases (NATs); NAA10; NAA15; NatA complex; Ogden syndrome; autism; congenital heart defects; intellectual disability; neurodevelopmental disorder.

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Figures

Figure 1
Figure 1
Pedigrees, Mild Facial Dysmorphology, and Hands of Individuals with Familial or de novo NAA15 LGD Variants (A) Pedigrees are shown for the three families with inherited variants. Family 10, Individual 10-1: at age 17 years and 6 months, with prominent eyebrows, broad nose, and prominent chin. Hand appears normal. Individual 10-2: at 6 years and 6 months, with very well-developed philtral pillars. Hand appears normal. Individual 10-3: mother, with long mentum of the chin and relatively thick alae nasi. Hand appears normal. Family 28, Individual 28-1: at age 15 years, partial syndactyly in one hand, but otherwise not with particularly notable dysmorphology. Individual 28-2: sister, at age 12 years, who was not noted to have any obvious dysmorphology. Individual 28-3: Mother at age 45 years, with broad nose but otherwise not with notable dysmorphology. (B) Minor facial dysmorphology was noted in some probands, but there were no reliably consistent features shared among them. Individual 2: at 17 years old, noted to have brachycephaly, appearance of ocular hypertelorism with short palpebral fissures, prominent nose tip with a longer columella of the nose, trapezoidal philtrum, and micrognathia without retrognathia. Also noted are small low-set, posteriorly rotated ears, with thickened and overfolded helix; hypoplastic distal phalanges on digits 2, 3, and 4; 5th finger with brachyclinodactyly; and persistence of fetal finger pads on the 3rd and 4th digit. Individual 8: at the age 8 years 9 months, noted to have thin philtrum, bulbous nasal tip, and 5th finger with brachyclinodactyly. Individual 13: at 4 years old, no facial dysmorphism noted. Individual 18: at 4 years and 3 months, with bulbous nose tip, thick alae nasi and anteverted nares, prominent cupid’s bow and philtrum, long mentum of the chin, and simple ears. Individual 31: with epicanthus inversus, smooth philtrum, thin vermilion border of the upper lip, and sparse lateral eyebrows.
Figure 2
Figure 2
Exonic Localization of NAA15 LGD Variants Identified in Subjects in This Study Schematic representation of the genomic structure of human NAA15. Solid blue rectangles indicate exons, and the horizontal bars represent introns. NAA15 variants with their relative positions in the gene are shown, and the number of affected individuals with the specific variants is shown in parentheses.
Figure 3
Figure 3
Expression Analysis of NAA15 in Research-Subject-Derived Cell Lines (A and D) Sanger sequencing of genomic DNA (top panel) and reverse-transcribed cDNA (bottom panel) isolated from a lymphoblastoid cell line (LCL) of individual 10-1 (c.239_240delAT) (A) and an induced pluripotent stem cell (iPS) line (passage 16) of individual 19 (c.1009_1012delGAAA) (D). (B and E) Quantification of different cDNA species from cDNA Sanger sequencing showing the relative ratio of WT NAA15 versus c.239_240delAT (LCL line) (B) and (c.1009_1012delGAAA) (passage 16 iPS cell line) (E). (C and F) NAA15 mRNA expression level analyzed by qPCR in research subject-derived cell lines (at passage numbers p10, p13, and p16), as compared to control cell lines (at passage 16). Error bars are standard deviation (SD), and the assay was performed three times per sample.
Figure 4
Figure 4
Truncation Mutations of Human NAA15 Impair NatA Function and Yeast Viability (A) Serial dilution spot assay depicting the sensitivity of human NAA15 Thr55Hisfs2 and Lys305 mutants to increased temperature in a ynaa10Δ, ynaa15Δ double-deletion background (yNatAΔ). (B) Confirmation of human NatA expression by immunoblot analysis with anti-hNAA10 and anti-HA (for HA-hNAA15 detection) along with anti-beta Actin as a loading control.

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