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M. Mori et al.
which one was an N-terminal splice site mutation and the other was a nonsense or missense mutation (Online Supplementary Figure S4C). Both of the two FANCD1 (BRCA2) splice site mutations (c.475+1G>A, c.517-2A>G) were regarded as deleterious. The one missense mutation (FANCD1 c.7847C>T/p.S2616F) was rated as “damaging” by both SIFT and PolyPhen-2 prediction programs. It is
notable that this missense mutation falls into the region termed “FA cluster” (amino acid position 2336-2729) where all of the five FA-D1-associated BRCA2 missense mutations are found.34 One FA-N patient had a homozy- gous splice mutation (c.3350+5C>T), resulting in skipping of exon 12 and C-terminal truncation (Figure 1D and Online Supplementary Figure S4D). This truncation may
Figure 3. The two FANCI variants in Case 96 caused two types of splicing defects. Real-time quantitative polymerase chain reaction (RT-PCR) analysis was carried out using a forward flanking primer on exon 3 and a reverse flanking primer on exon 5 as indicated. Two types of products were obtained, and the sequencing analyses revealed a single nucleotide insertion (top) and exon 4 skipping (bottom).
Table 4. Clinical features of Japanese Fanconi anemia (FA)-D1 and FA-N cases.
Individual
Sex
FA mutations
FA-features
Chromosome breakage test ALDH2 genotype Hematologic abnormality (onset)
Solid tumors (onset)
Outcome
Case 65
Female
FANCD1
c.517-2A>G,
c.6952C>T: p.R2318X Short stature Left thumb polydactyly Right renal agenesis Microphthalmus Microcephaly Positive (MMC) GG
None
Immature teratoma (9 months old)
Case 66
Male
FANCD1
c.475+1G>A
c.7847C>T:p.S2616F Short stature Microcephaly
Positive (MMC) GA
None
Case 98
Male
FANCN
c.3350+5C>T
c.3350+5C>T
Short stature
ASD, PDA
Congenital absence of inferior vena cava, Congenital tracheal stenosis Microcephaly
Positive (DEB)
GA
None
AP37P*
Male
FANCD1
c.-40+1G>A,
c.8504C>A: p.S2835X Short stature Mid-face hypoplasia Sprengel’s deformity Multiple café-au-lait spots
Positive (MMC) GG
Acute myeloid leukemia (2 years old) None
Died of leukemia at 2 years old
T-lymphoblastic lymphoma, Adenosquamous lung carcinoma (23 years old)
Died of
Wilms
tumor (1 year old)
Died of Wilms tumor at 1.5 years old
Alive with progressive
teratoma at 1.7 years old lymphoma at
*a previously reported case.32 MMC, mitomycin C, Other abbreviations are explained in Table 2 and 3.
25.5 years old
1970
haematologica | 2019; 104(10)