3.2 | Mutation analysis of EDAR and EDA1
After diagnosis, we aimed to determine the causative gene. After
screening the coding sequences of the EDA1 gene by PCR, no
mutation was found in Family 4. We found a new EDAR mutation
c.338G>A (Cys113Tyr) by using whole exome sequencing
technology by ”MAF<1%” and ”exonic” filtering. SIFT,
Polyphen2 and MutationTaster predictions for the mutation were
“deleterious” (0.00), “probably damaging” (0.996), and
“disease-causing” (1.00), respectively, suggesting the variant was
highly pathogenic. Candidate mutation was then confirmed for proband 4
and his mother by Sanger sequencing (Figure 2B), while his father and
brother were wild type at this location. A cross-species amino acid
sequence alignment of EDAR showed that the mutation site was highly
conserved among humans (>NP_071731.1), cattle
(>XP_005212787.1), zebrafish
(>NP_001108536.2), rhesus monkeys
(>XP_014968589.2), dogs (>XP_005626028.2),
mice (>NP_034230.1), and chickens
(>NP_001012629.1) (Figure 2C).
Three of the mutations found in oligodontia patients have previously
been reported in EDA1 exons: c.865C>T
(Arg289Cys)(Song et al., 2009);
c.866G>A(Arg289His)(Ruiz-Heiland
et al., 2016); and c.1013C>T
(Thr338Met)(Han et al., 2008) (Figure 3),
all of which are located in the TNF domain. In patient 1, the
p.Arg289Cys (c.865C>T) mutation occurs in exon 7 ofEDA1 , changing codon 289 from encoding Arg to Cys. A p.Arg289His
(c.866G>A) mutation was found in exon 7 of EDA1 of
patient 2, changing codon 289 from encoding Arg to His. For patient 3,
there was a p.Thr338Met (c.1013C>T) mutation in exon 8 ofEDA1 , changing codon 338 from encoding Thr to Met.
3.3 |Phenotypes
of NSTA patients with EDAR mutations
We reviewed four published studies and summarized data fromEDAR -related NSTA patients with a total of seven EDARmutations(Arte et al., 2013;
Jonsson et al., 2018;
Mumtaz et al., 2020;
Zeng et al., 2017). The mutation sites of
the EDAR gene, protein changes, and the types of mutations are
given in Table 1. The details of the missing teeth are listed in Table
2.
In
NSTA patients with EDAR mutations, the maxillary lateral incisor
had the highest missing rate (83.3%), followed by the mandibular
lateral incisor (43.3%), the mandibular central incisor (40.0%), and
the second premolars (33.3%); although this does not include the third
molars. The missing rate of the maxillary first premolars is lowest
(6.7%), followed by the mandibular canines (10%). In all, the rate of
loss of the molars is lower than that of anterior teeth (Figure 4).