A syndrome of congenital microcephaly, intellectual disability and dysmorphism with a homozygous mutation in FRMD4A.
A consanguineous Bedouin Israeli kindred presented with a novel autosomal recessive intellectual disability syndrome of congenital microcephaly, low anterior hairline, bitemporal narrowing, low-set protruding ears, strabismus and tented thick eyebrows with sparse hair in their medial segment. Brain imaging demonstrated various degrees of agenesis of corpus callosum and hypoplasia of the vermis and cerebellum. Genome-wide linkage analysis followed by fine mapping defined a 7.67 Mb disease-associated locus (LOD score 4.99 at θ=0 for marker D10S1653). Sequencing of the 48 genes within the locus identified a single non-synonymous homozygous duplication frameshift mutation of 13 nucleotides (c.2134_2146dup13) within the coding region of FRMD4A, that was common to all affected individuals and not found in 180 non-related Bedouin controls. Three of 50 remotely related healthy controls of the same tribe were heterozygous for the mutation. FRMD4A, member of the FERM superfamily, is involved in cell structure, transport and signaling. It regulates cell polarity by playing an important role in the activation of ARF6, mediating the interaction between Par3 and the ARF6 guanine nucleotide exchange factor. ARF6 is known to modulate cell polarity in neurons, and regulates dendritic branching in hippocampal neurons and neurite outgrowth. The FRMD4 domain that is essential for determining cell polarity through interaction with Par3 is truncated by the c.2134_2146dup13 mutation. FRMD4A polymorphisms were recently suggested to be a risk factor for Alzheimer's disease. We now show a homozygous frameshift mutation of the same gene in a severe neurologic syndrome with unique dysmorphism.
The Morris Kahn Laboratory of Human Genetics, National Institute for Biotechnology in the Negev and Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel.
Dina
D
Fine
Zusman Child Development Center, Pediatric Division, Soroka University Medical Center and Ben-Gurion University of the Negev, Beer-Sheva, Israel.
Hagit
H
Flusser
The Morris Kahn Laboratory of Human Genetics, National Institute for Biotechnology in the Negev and Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel.
Barak
B
Markus
Pediatric Neurology unit, Pediatric Division, Soroka University Medical Center and Ben-Gurion University of the Negev, Beer-Sheva, Israel.
Zamir
Z
Shorer
Department of Ophthalmology, Soroka University Medical Center and Clalit Health Services, Ben-Gurion University of the Negev, Beer-Sheva, Israel.
Libe
L
Gradstein
The Morris Kahn Laboratory of Human Genetics, National Institute for Biotechnology in the Negev and Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel.
Shareef
S
Khateeb
The Morris Kahn Laboratory of Human Genetics, National Institute for Biotechnology in the Negev and Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel.
Yshia
Y
Langer
The Morris Kahn Laboratory of Human Genetics, National Institute for Biotechnology in the Negev and Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel.
Ginat
G
Narkis
Faculty of Health Sciences, Department of Nutrition, Ariel University, Ariel, Israel.
Ruth
R
Birk
Zusman Child Development Center, Pediatric Division, Soroka University Medical Center and Ben-Gurion University of the Negev, Beer-Sheva, Israel.
Aharon
A
Galil
Department of Diagnostic Imaging, Soroka Medical Center, Beer-Sheva, Israel.
Ilan
I
Shelef
The Morris Kahn Laboratory of Human Genetics, National Institute for Biotechnology in the Negev and Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel.|Soroka Medical Center, Genetics Institute, Beer-Sheva, Israel.
Ohad S
OS
Birk
D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics*; D000328:Adult; D000595:Amino Acid Sequence; D001483:Base Sequence; D002648:Child; D005260:Female; D016368:Frameshift Mutation; D020440:Gene Duplication; D006720:Homozygote; D006801:Humans; D008607:Intellectual Disability / Q000175:diagnosis / Q000235:genetics*; D008297:Male; D008831:Microcephaly / Q000175:diagnosis / Q000235:genetics*; D008969:Molecular Sequence Data; D013577:Syndrome
D048868:Adaptor Proteins, Signal Transducing; C574784:FERM domain-containing protein 4A, human