Presented by Sébastien BENDER

Contribution in the understanding of the molecular mechanisms in Heavy Chain

Deposition Disease

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Any direct financial payments including receipt of honoraria

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Heavy Chain Deposition Disease =HCDD

Molecular mechanisms of HCDD

Healthy glomerulus Sclerotic glomerulus

▪ Deposition of a truncated heavy chain (HC), mainly in the kidney.▪ Non-organized/amorphous deposits along tubular and glomerular

basement membranes.▪ Proteinuria. ▪ Nodular glomerulosclerosis.

3

VDJ CH1 CH2 CH3

Normal 1

H

γ1 case 1

CH1 deletion is always present in HCDD

4

Molecular mechanisms of HCDD

= Binding Ig Protein

5

Molecular mechanisms of HCDD

Can CH1 deletion occur due to a problem with the light chain (LC)?

6

Molecular mechanisms of HCDD

7

Molecular mechanisms of HCDD

Identification of 2 monoclonal components

Gamma heavy chain

Serum

The 2 components are produced by the same clone

@human gamma @human lambdaMerge

BM

Lambda light chain

BM Serum

8

Molecular mechanisms of HCDD

The lambda light chain has its V domain truncated

λmRNA atggcctgggctctgctgctcctcaccctcctcactcagggcacaggatcctgggctcagtctgccctgactcagcctccctccgtgtccgggtctcctggacagtcagtcaccatctcc

Prot M A W A L L L L T L L T Q G T G S W A Q S A L T Q P P S V S G S P G Q S V T I S

λmRNA tgcactggaatcagcagtgacgttggtcagcccaaggctgccccctcggtcactctgttcccaccctcctctgaggagcttcaagccaacaaggccacactggtgtgtctcataagtgac

Prot C T G I S S D V G Q P K A A P S V T L F P P S S E E L Q A N K A T L V C L I S D

λmRNA ttctacccgggagccgtgacagtggcctggaaggcagatagcagccccgtcaaggcgggagtggagaccaccacaccctccaaacaaagcaacaacaagtacgcggccagcagctacctg

Prot F Y P G A V T V A W K A D S S P V K A G V E T T T P S K Q S N N K Y A A S S Y L

λmRNA agcctgacgcctgagcagtggaagtcccacaaaagctacagctgccaggtcacgcatgaagggagcaccgtggagaagacagtggcccctacagaatgttcatag

Prot S L T P E Q W K S H K S Y S C Q V T H E G S T V E K T V A P T E C S -

Leader FR1

CDR1 Cλ3

Cλ3

Cλ3

VC junction

+22nt

-19nt

V J Cλ3L

Protein

gDNA

cDNA

L V Cλ3

9

Molecular mechanisms of HCDD

CH1 deletion of the heavy chain is genomic

VDJ CH1 CH2 CH3

Normal 1

H

γ1 case 1

B C

Protein

gDNA

cDNA

H CH2VDJ CH1 CH3Sµ-Sγ1L

L VDJ H CH2 CH3

10

Molecular mechanisms of HCDD

Is the truncated LC can associate with a HC ?

FL

+

FL

control +

0

2 0 0 0

4 0 0 0

6 0 0 0

[ I g G ] i n c u t u r e s u p e r n a t a n t s

[Ig

G

] in

n

g/m

L

ND

ɣFL

λcontrol Δλ

ɣFL

??

11

Molecular mechanisms of HCDD

Is the CH1 deletion beneficial to the plasma cell ?

ɣFL Δɣ

)

(+

)

FL(+

+)(

FL+)

(

0

20

40

60

80

0

5

10

15

20

HC secretion

**

ns

[ ]

intr

acell

ula

r/secre

ted

[] in

tracellu

laire

/sécré

té

+

FL+

0.0

0.5

1.0

1.5

2.0

2.5

*

Stress marker Xbp1-s expression in sp2/0 clones

Rela

tive

mR

NA

exp

ressio

n

Xbp1-s

Δλ+OR

12

Molecular mechanisms of HCDD

PROLIFERATION

Immunoglobulin

PLASMA CELL

Truncatedheavy chain

Truncated light chain

Oncogenics events

L VDJ CH1 H CH2 CH3

L VJλ Cλ+1

L VDJ CH1 H CH2 CH3

L Vλ Cλ+2

L VDJ H CH2 CH3

L Vλ Cλ+3

13

Molecular mechanisms of HCDD

A new model to mimic the loss of the light chain

L VJk Ck

LoxPLoxP

Light chain of Fanconisyndrome mouse model

Recombinase CRE induction

L VDJ H CH2 CH3CH1

Ck

? 14

Molecular mechanisms of HCDD

Mouse heavy chain

Light chain of Fanconi syndrome mouse model (deleted)

Conclusion

15

▪ We showed that deletion of the LC could be the first event leading to the generation of a truncated heavy chain in HCDD

▪ Results must be confirmed in other HCDD patients

▪ Regarding the mouse model first tests are ongoing

Thank you for your attention

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Pr Christophe Sirac Pr Arnaud Jaccard

Pr Frank Bridoux

Dr Vincent Javaugue Maria Victoria Ayala Amélie BONAUD

Pr Guy Touchard