Alternative Gene Splicing in Myeloma:
Aberrant Splicing of Hyaluronan Synthase 1
Predicts for Poor Survival
Linda M. Pilarski
University of Alberta/Cross Cancer Institute

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MM Includes "Early Stage" B Cells and
Terminally Differentiated Plasma Cells

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MM is characterized by extensive
genetic abnormalities in plasma cells
1. Chromosomal abnormalities
- structural abnormalities
- numeric abnormalities
2. Recurrent illegitimate switch region
translocations- may be among the
primary events in MM.
3. Multiple abnormalities per patient

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MM B Cells Exhibit Chromosomal Abnormalities
(Poster by Carina Debes Marun PO.208)
t(4;14)+
fusion
fusion
MM Lymphocyte
A
Single Ch13
CD20+ MM B cell
with Ch13
Diploid Ch 5
MM Lympocyte
with Ch13 and
diploid Ch5
Single Ch13

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Genetic Abnormalities in MM B cells
- Aberrant splicing of Hyaluronan Synthase 1 (HAS1)
27/58 patients (47%), correlates with poor survival
HAS1 and its variants are expressed only
in MM B cells.
Is there a causative link between
these abnormalities?
Do abnormalities in HAS1 lead to
chromosomal abnormalities?

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Splice Variants of HAS1 (578 aa full length)
ATG
TGA
HAS1Va
1
2
3
5
56
329 aa
bp
ATG
TGA
59 93 bp
HAS1Vb
bp
1
2
3
5
361 aa
ATG
TAA
26
bp
HAS1Vc
1
2
3
4
354 aa
(See Poster by Sophia Adamia PO.127)

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HAS1 variants are clinically important
- HAS1Vb correlates with poor survival
- HAS1Vb is the first reported prognostic
marker for blood-borne malignant B cells

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Allelic Homozygosity of a HAS1
SNP characterizes MM patients
HAS1 SNP homozygosity
defines the patient germline:
Sorted T cells had the same HAS1 alleles
as sorted malignant B cells or BM plasma cells
Bioinformatic analysis and direct evidence
suggests that HAS1 SNPs and mutations
lead to aberrant HAS1 splicing

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Splicing SNPs in concert with recurrent genetic
variations in classical splice sites, exonic & intronic
elements create or activate cryptic splice sites.
Regulatory
SF
SF
complex
ag
4
gu
ag
5
A (Y)
A (Y)
n
n
Intronic elements
Exonic elements
Classical splice sites
SF
SF
4
gu
ag
5
A (Y)
A (Y)n
n
Create/activate cryptic splice sites

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HAS1 splicing patterns have a strong impact on
clinical outcome: genomic HAS1 abnormalities
may predispose to disease
-
Germline SNPs in HAS1, together with recurrent
HAS1 mutations in malignant B cells, alter
splicing of HAS1 transcripts
-
Aberrant HAS1 splicing creates novel
HAS1 splice variants that contribute to reduced
survival
In MM, the HAS1 splicing pattern, not absolute
overexpression, is the indicator of clinical outcome.

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Aberrant HAS1 splicing may facilitate emergence
of genetic variants and more aggressive disease
RHAMM-mediated centrosomal abnormalities
lead to chromosomal instability. Most
such cells die.
Aberrant HAS1 splicing leads to
intracellular HA, competition for centrosomal
targeting sites and escape from apoptosis
caused by high levels of RHAMM.
HAS1 variant-enabled rescue of RHAMM
overexpressors leads to aggressive genetic
variants, progressive MM and short survival.

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Sophia Adamia
Andrew Belch
Funded by NIH and CIHR

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